Difference of Squares Formula

The difference of squares formula is another key algebraic shortcut that simplifies expressions involving two squared terms subtracted from each other. It is written as:

(XY)2=X22XY+Y2(X - Y)^2=X^2 - 2XY + Y^2
This formula skips the need for full expansion and directly factors the expression. It works for both numerical and algebraic expressions, making it versatile in solving equations and simplifying terms. That is, when we encounter two numbers with a minus sign between them, that is, the difference and they will be in parentheses and raised as a squared expression, we can use this formula.

For (xy)2(x - y)^2 the full expansion would be:
(xy)2=(xy)(xy)=xx+x(y)yxy(y)=x22xy+y2(x - y)^2=(x-y)(x−y)=x⋅x+x⋅(-y)-y⋅x−y⋅(-y)=x^2-2xy+y^2

Visual breakdown of abbreviated multiplication formulas: (a+b)² = a² + 2ab + b² and (a−b)² = a² − 2ab + b², with color-coded area models representing the expansion of binomials

Example:

(a4)2=(a - 4)^2=
a×a+a×(4)+(4)×a+(4)×(4)=a\times a+a\times (-4)+ (-4)\times a + (-4) \times (-4) =
a2+2(4a)+(4)2=a^2+2(-4a)+ (-4)^2 =
a28a+16a^2-8a+16

Suggested Topics to Practice in Advance

  1. The formula for the Sum of Squares

Practice Square of Difference

Examples with solutions for Square of Difference

Exercise #1

(4b3)(4b3) (4b-3)(4b-3)

Rewrite the above expression as an exponential summation expression:

Video Solution

Step-by-Step Solution

To solve this problem, we will apply the square of a binomial formula.

The given expression is (4b3)(4b3)(4b-3)(4b-3). We recognize this as the square of a binomial, which can be rewritten as (4b3)2(4b-3)^2. To expand this expression, we use the formula:

(ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2

In our expression, a=4ba = 4b and b=3b = 3. Let's apply the formula:

  • Calculate a2a^2:
    a2=(4b)2=16b2a^2 = (4b)^2 = 16b^2
  • Calculate 2ab-2ab:
    2ab=2(4b)(3)=24b-2ab = -2(4b)(3) = -24b
  • Calculate b2b^2:
    b2=(3)2=9b^2 = (3)^2 = 9

Putting it all together, we have:

(4b3)2=16b224b+9(4b-3)^2 = 16b^2 - 24b + 9

Therefore, the exponential summation expression is (4b3)2(4b-3)^2, with the expanded form:

16b224b+916b^2 - 24b + 9

This matches choice 3, confirming our solution.

Answer

(4b3)2 (4b-3)^2

16b224b+9 16b^2-24b+9

Exercise #2

Rewrite the following expression as an addition and as a multiplication:

(3xy)2 (3x-y)^2

Video Solution

Step-by-Step Solution

To solve this problem, let's start by identifying the parts of the binomial:

  • The expression (3xy)2(3x-y)^2 represents a binomial squared.
  • We recognize it has the form (ab)2(a-b)^2 where a=3xa = 3x and b=yb = y.
  • Using the formula for the square of a difference: (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2, we find the expanded form.

Let's apply the formula:

Step 1: Expand (3xy)2(3x-y)^2 using the formula:
(3xy)2=(3x)22(3x)(y)+y2(3x-y)^2 = (3x)^2 - 2(3x)(y) + y^2

Step 2: Calculate each part:
(3x)2=9x2(3x)^2 = 9x^2
2(3x)(y)=6xy-2(3x)(y) = -6xy
y2y^2 stays as y2y^2

Step 3: Combine these results to get the addition form:
9x26xy+y29x^2 - 6xy + y^2

The expression in multiplication form, as provided, is just repeating the factors:
(3xy)(3xy)(3x-y)(3x-y)

Therefore, the expression rewritten as addition is 9x26xy+y29x^2 - 6xy + y^2 and as multiplication (3xy)(3xy)(3x-y)(3x-y).

Answer

9x26xy+y2 9x^2-6xy+y^2

(3xy)(3xy) (3x-y)(3x-y)

Exercise #3

(a4)(a4)=? (a-4)(a-4)=\text{?}

Video Solution

Step-by-Step Solution

To solve the problem, we will expand the expression (a4)(a4)(a-4)(a-4) using the square of a difference formula.

This formula states: (xy)2=x22xy+y2(x-y)^2 = x^2 - 2xy + y^2.
In our case, x=ax = a and y=4y = 4, so we apply the formula:

  • First term: x2=a2x^2 = a^2
  • Second term: 2xy=2a4=8a-2xy = -2 \cdot a \cdot 4 = -8a
  • Third term: y2=42=16y^2 = 4^2 = 16

Putting it all together, the expression becomes:
a28a+16a^2 - 8a + 16.

After matching this result with the given choices, we find it corresponds to choice 4.

Therefore, the solution to the problem is a28a+16\mathbf{a^2 - 8a + 16}.

Answer

a28a+16 a^2-8a+16

Exercise #4

Declares the given expression as a sum

(7b3x)2 (7b-3x)^2

Video Solution

Step-by-Step Solution

To solve for (7b3x)2(7b - 3x)^2 as a sum, we'll follow these steps:

  • Step 1: Identify the given expression and apply the formula for the square of a difference:
    (ab)2=a22ab+b2(a - b)^2 = a^2 - 2ab + b^2 where a=7ba = 7b and b=3xb = 3x.
  • Step 2: Expand each term:
    • a2=(7b)2=49b2a^2 = (7b)^2 = 49b^2
    • 2ab=2×7b×3x=42bx-2ab = -2 \times 7b \times 3x = -42bx
    • b2=(3x)2=9x2b^2 = (3x)^2 = 9x^2
  • Step 3: Combine all terms to form the sum:
    (7b3x)2=49b242bx+9x2 (7b - 3x)^2 = 49b^2 - 42bx + 9x^2 .

Therefore, the solution to the problem is (7b3x)2=49b242bx+9x2(7b - 3x)^2 = 49b^2 - 42bx + 9x^2.

Hence, the correct answer choice is: 49b242bx+9x2 49b^2 - 42bx + 9x^2

Answer

49b242bx+9x2 49b^2-42bx+9x^2

Exercise #5

Choose the expression that has the same value as the following:

(xy)2 (x-y)^2

Video Solution

Step-by-Step Solution

We use the abbreviated multiplication formula:

(xy)(xy)= (x-y)(x-y)=

x2xyyx+y2= x^2-xy-yx+y^2=

x22xy+y2 x^2-2xy+y^2

Answer

x22xy+y2 x^2-2xy+y^2

Exercise #6

Choose the expression that has the same value as the following:

(x7)2 (x-7)^2

Video Solution

Step-by-Step Solution

To solve the problem, we need to expand the expression (x7)2(x-7)^2 using the formula for the square of a difference.

The formula for the square of a difference is (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2.

Let's apply this formula to our expression (x7)2(x-7)^2:

  • Identify a=xa = x and b=7b = 7.
  • Substitute these values into the formula: (x7)2=x22(x)(7)+72(x-7)^2 = x^2 - 2(x)(7) + 7^2.
  • Calculate each term:
    • x2x^2 remains as x2x^2.
    • 2(x)(7)=14x-2(x)(7) = -14x.
    • 72=497^2 = 49.

So, expanding the expression, we get x214x+49x^2 - 14x + 49.

Thus, the expression that has the same value as (x7)2(x-7)^2 is x214x+49x^2 - 14x + 49.

Answer

x214x+49 x^2-14x+49

Exercise #7

(x26)2= (x^2-6)^2=

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify a and b in the expression (x26)2 (x^2 - 6)^2 .
  • Step 2: Apply the square of a difference formula.
  • Step 3: Simplify the resulting expression.

Now, let's work through each step:
Step 1: The expression is (x26)2 (x^2 - 6)^2 . Here, a=x2 a = x^2 and b=6 b = 6 .
Step 2: Apply the binomial formula: (ab)2=a22ab+b2 (a - b)^2 = a^2 - 2ab + b^2 .
Step 3:
1. Calculate a2 a^2 :
a2=(x2)2=x4 a^2 = (x^2)^2 = x^4 .
2. Calculate 2ab 2ab :
2ab=2(x2)(6)=12x2 2ab = 2(x^2)(6) = 12x^2 .
3. Calculate b2 b^2 :
b2=62=36 b^2 = 6^2 = 36 .
4. Substitute these back into the formula:
(x26)2=x412x2+36(x^2 - 6)^2 = x^4 - 12x^2 + 36.

Therefore, the expanded expression is x412x2+36 x^4 - 12x^2 + 36 .

Answer

x412x2+36 x^4-12x^2+36

Exercise #8

(xx2)2= (x-x^2)^2=

Video Solution

Step-by-Step Solution

To solve the expression (xx2)2(x-x^2)^2, we will use the square of a binomial formula (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2.

Let's identify aa and bb in our expression:

  • Here, a=xa = x and b=x2b = x^2.

Applying the formula:

(xx2)2=(x)22(x)(x2)+(x2)2(x - x^2)^2 = (x)^2 - 2(x)(x^2) + (x^2)^2

Calculating each part, we get:

  • (x)2=x2(x)^2 = x^2
  • 2(x)(x2)=2x3-2(x)(x^2) = -2x^3
  • (x2)2=x4(x^2)^2 = x^4

Combining these results, the expression simplifies to:

x42x3+x2x^4 - 2x^3 + x^2

Therefore, the expanded form of (xx2)2(x-x^2)^2 is x42x3+x2\boxed{x^4 - 2x^3 + x^2}.

Answer

x42x3+x2 x^4-2x^3+x^2

Exercise #9

9x212x+4= 9x^2-12x+4=

Video Solution

Step-by-Step Solution

To rewrite the expression 9x212x+4 9x^2 - 12x + 4 as a perfect square, follow these steps:

  • Step 1: Compare the expression 9x212x+4 9x^2 - 12x + 4 with (ab)2(a - b)^2.
  • Step 2: Note that (ab)2=a22ab+b2(a - b)^2 = a^2 - 2ab + b^2.
  • Step 3: Identify matching terms: a2=9x2a^2 = 9x^2, 2ab=12x-2ab = -12x, b2=4b^2 = 4.

Now, separate this into steps:
Step 1: Set a2=9x2a^2 = 9x^2, so a=3xa = 3x.
Step 2: Set b2=4b^2 = 4, so b=2b = 2.
Step 3: Verify 2ab=12x-2ab = -12x:
2×3x×2=12x.-2 \times 3x \times 2 = -12x.
This confirms our values of aa and bb are correct.

Thus, the expression 9x212x+4 9x^2 - 12x + 4 is equivalent to the square (3x2)2(3x - 2)^2.

The correct choice is: (3x2)2 (3x-2)^2 .

Answer

(3x2)2 (3x-2)^2

Exercise #10

x22x+1=9 x^2-2x+1=9

Solve using the abbreviated multiplication formula

Video Solution

Step-by-Step Solution

We will solve the quadratic equation x22x+1=9 x^2 - 2x + 1 = 9 using the square of a binomial formula.

Firstly, let's recognize that the left side of the equation forms a perfect square:

x22x+1(x1)2 x^2 - 2x + 1 \equiv (x - 1)^2

Therefore, the equation can be rewritten as:

(x1)2=9(x - 1)^2 = 9

To solve for x x , take the square root of both sides. Remember to consider both the positive and negative solutions from the square root:

Thus, x1=±3 x - 1 = \pm 3

This gives us two separate equations to solve:

  • x1=3 x - 1 = 3
  • x1=3 x - 1 = -3

Solving each equation for x x gives:

  • For x1=3 x - 1 = 3 :
  • Add 1 to both sides: x=4 x = 4

  • For x1=3 x - 1 = -3 :
  • Add 1 to both sides: x=2 x = -2

Therefore, the solutions to the equation are x=4 x = 4 and x=2 x = -2 .

Comparing these solutions to the given answer choices, we identify the correct choice as:

x=2 x=-2 or x=4 x=4

In conclusion, the solutions to the equation are x=4 x = 4 and x=2 x = -2 .

Answer

x=2 x=-2 o x=4 x=4

Exercise #11

Solve the following problem:

x2+144=24x x^2+144=24x

Video Solution

Step-by-Step Solution

Proceed to solve the given equation:

x2+144=24x x^2+144=24x

Arrange the equation by moving terms:

x2+144=24xx224x+144=0 x^2+144=24x \\ x^2-24x+144=0

Note that we are able to factor the expression on the left side by using the perfect square trinomial formula:

(ab)2=a22ab+b2 (\textcolor{red}{a}-\textcolor{blue}{b})^2=\textcolor{red}{a}^2-2\textcolor{red}{a}\textcolor{blue}{b}+\textcolor{blue}{b}^2

As demonstrated below:

144=122 144=12^2

Therefore, we'll represent the rightmost term as a squared term:

x224x+144=0x224x+122=0 x^2-24x+144=0 \\ \downarrow\\ \textcolor{red}{x}^2-24x+\textcolor{blue}{12}^2=0

Now let's examine once again the perfect square trinomial formula mentioned earlier:

(ab)2=a22ab+b2 (\textcolor{red}{a}-\textcolor{blue}{b})^2=\textcolor{red}{a}^2-\underline{2\textcolor{red}{a}\textcolor{blue}{b}}+\textcolor{blue}{b}^2

And the expression on the left side in the equation that we obtained in the last step:

x224x+122=0 \textcolor{red}{x}^2-\underline{24x}+\textcolor{blue}{12}^2=0

Note that the terms x2,122 \textcolor{red}{x}^2,\hspace{6pt}\textcolor{blue}{12}^2 indeed match the form of the first and third terms in the perfect square trinomial formula (which are highlighted in red and blue),

However, in order to factor this expression (which is on the left side of the equation) using the perfect square trinomial formula mentioned, the remaining term must also match the formula, meaning the middle term in the expression (underlined):

(ab)2=a22ab+b2 (\textcolor{red}{a}-\textcolor{blue}{b})^2=\textcolor{red}{a}^2-\underline{2\textcolor{red}{a}\textcolor{blue}{b}}+\textcolor{blue}{b}^2

In other words - we'll query whether we can represent the expression on the left side of the equation as:

x224x+122=0?x22x12+122=0 \textcolor{red}{x}^2-\underline{24x}+\textcolor{blue}{12}^2=0\\ \updownarrow\text{?}\\ \textcolor{red}{x}^2-\underline{2\cdot\textcolor{red}{x}\cdot\textcolor{blue}{12}}+\textcolor{blue}{12}^2=0

And indeed it is true that:

2x12=24x 2\cdot x\cdot12=24x

Therefore we can represent the expression on the left side of the equation as a perfect square trinomial:

x22x12+122=0(x12)2=0 \textcolor{red}{x}^2-\underline{2\cdot\textcolor{red}{x}\cdot\textcolor{blue}{12}}+\textcolor{blue}{12}^2=0 \\ \downarrow\\ (\textcolor{red}{x}-\textcolor{blue}{12})^2=0

From here we can take the square root of both sides of the equation (and don't forget that there are two possibilities - positive and negative when taking an even root of both sides of an equation), then we'll easily solve by isolating the variable:

(x12)2=0/x12=±0x12=0x=12 (x-12)^2=0\hspace{8pt}\text{/}\sqrt{\hspace{6pt}}\\ x-12=\pm0\\ x-12=0\\ \boxed{x=12}

Let's summarize the solution of the equation:

x2+144=24xx224x+144=0x22x12+122=0(x12)2=0x12=0x=12 x^2+144=24x \\ x^2-24x+144=0 \\ \downarrow\\ \textcolor{red}{x}^2-2\cdot\textcolor{red}{x}\cdot\textcolor{blue}{12}+\textcolor{blue}{12}^2=0 \\ \downarrow\\ (\textcolor{red}{x}-\textcolor{blue}{12})^2=0 \\ \downarrow\\ x-12=0\\ \downarrow\\ \boxed{x=12}

Therefore the correct answer is answer C.

Answer

x=12 x=12

Exercise #12

Solve the following problem:

x2=6x9 x^2=6x-9

Video Solution

Step-by-Step Solution

Proceed to solve the given equation:

x2=6x9 x^2=6x-9

First, let's arrange the equation by moving terms:

x2=6x9x26x+9=0 x^2=6x-9 \\ x^2-6x+9=0

Note that we can factor the expression on the left side by using the perfect square trinomial formula for a binomial squared:

(ab)2=a22ab+b2 (\textcolor{red}{a}-\textcolor{blue}{b})^2=\textcolor{red}{a}^2-2\textcolor{red}{a}\textcolor{blue}{b}+\textcolor{blue}{b}^2

As shown below:

9=32 9=3^2 Therefore, we'll represent the rightmost term as a squared term:

x26x+9=0x26x+32=0 x^2-6x+9=0 \\ \downarrow\\ \textcolor{red}{x}^2-6x+\textcolor{blue}{3}^2=0

Now let's examine again the perfect square trinomial formula mentioned earlier:

(ab)2=a22ab+b2 (\textcolor{red}{a}-\textcolor{blue}{b})^2=\textcolor{red}{a}^2-\underline{2\textcolor{red}{a}\textcolor{blue}{b}}+\textcolor{blue}{b}^2

And the expression on the left side in the equation that we obtained in the last step:

x26x+32=0 \textcolor{red}{x}^2-\underline{6x}+\textcolor{blue}{3}^2=0

Note that the terms x2,32 \textcolor{red}{x}^2,\hspace{6pt}\textcolor{blue}{3}^2 indeed match the form of the first and third terms in the perfect square trinomial formula (which are highlighted in red and blue),

However, in order to factor the expression in question (which is on the left side of the equation) using the perfect square trinomial formula mentioned, the remaining term must also match the formula, meaning the middle term in the expression (underlined with a single line):

(ab)2=a22ab+b2 (\textcolor{red}{a}-\textcolor{blue}{b})^2=\textcolor{red}{a}^2-\underline{2\textcolor{red}{a}\textcolor{blue}{b}}+\textcolor{blue}{b}^2

In other words - we will query whether we can represent the expression on the left side of the equation as:

x26x+32=0?x22x3+32=0 \textcolor{red}{x}^2-\underline{6x}+\textcolor{blue}{3}^2=0\\ \updownarrow\text{?}\\ \textcolor{red}{x}^2-\underline{2\cdot\textcolor{red}{x}\cdot\textcolor{blue}{3}}+\textcolor{blue}{3}^2=0

And indeed it is true that:

2x3=6x 2\cdot x\cdot3=6x

Therefore we can represent the expression on the left side of the equation as a perfect square binomial:

x22x3+32=0(x3)2=0 \textcolor{red}{x}^2-\underline{2\cdot\textcolor{red}{x}\cdot\textcolor{blue}{3}}+\textcolor{blue}{3}^2=0 \\ \downarrow\\ (\textcolor{red}{x}-\textcolor{blue}{3})^2=0

From here we can take the square root of both sides of the equation (and don't forget that there are two possibilities - positive and negative when taking an even root of both sides of an equation), then we'll easily solve by isolating the variable:

(x3)2=0/x3=±0x3=0x=3 (x-3)^2=0\hspace{8pt}\text{/}\sqrt{\hspace{6pt}}\\ x-3=\pm0\\ x-3=0\\ \boxed{x=3}

Let's summarize the solution of the equation:

x2=6x9x26x+9=0x22x3+32=0(x3)2=0x3=0x=3 x^2=6x-9 \\ x^2-6x+9=0 \\ \downarrow\\ \textcolor{red}{x}^2-2\cdot\textcolor{red}{x}\cdot\textcolor{blue}{3}+\textcolor{blue}{3}^2=0 \\ \downarrow\\ (\textcolor{red}{x}-\textcolor{blue}{3})^2=0 \\ \downarrow\\ x-3=0\\ \downarrow\\ \boxed{x=3}

Therefore the correct answer is answer C.

Answer

x=3 x=3

Exercise #13

Fill in the blanks:

x2+?+9=(x3)2 x^2+?+9=(x-3)^2

Video Solution

Step-by-Step Solution

To address this mathematical problem, we will apply the square of a binomial formula and solve for the missing term. Here's how:

  • Step 1: Expand the right-hand side of the equation (x3)2(x-3)^2.
  • Step 2: Equate the expanded form to x2+?+9x^2 + ? + 9.
  • Step 3: Solve for the missing term by comparing the coefficients.

Step 1: Expanding (x3)2(x-3)^2 using the formula, we get:

(x3)2=x22x3+32 (x - 3)^2 = x^2 - 2 \cdot x \cdot 3 + 3^2 .

This simplifies to:

x26x+9 x^2 - 6x + 9 .

Step 2: Equating this to the left-hand side:

x2+?+9=x26x+9 x^2 + ? + 9 = x^2 - 6x + 9 .

Step 3: Compare the terms:

The term that replaces "?" on the left-hand side must make the equation hold.

Setting corresponding terms equal, we find that:

?=6x ? = -6x .

Therefore, the solution to the problem is 6x -6x .

Answer

6x -6x

Exercise #14

Fill in the blanks:

(2x?)2=4x212x+? (2x-?)^2=4x^2-12x+\text{?}

Video Solution

Step-by-Step Solution

To solve the problem, we'll follow these steps:

  • Step 1: Identify the given form and match it with the square of a difference formula
  • Step 2: Determine the values of 'a' and 'b' such that the expanded form matches both sides of the equation
  • Step 3: Calculate the missing value in the expression

Now, let's work through each step:
Step 1: We are given the expression (2x?)2=4x212x+? (2x-?)^2=4x^2-12x+\text{?} .
Step 2: Using the standard formula for a perfect square expansion:
(2xb)2=(2x)222xb+b2=4x24xb+b2(2x-b)^2 = (2x)^2 - 2 \cdot 2x \cdot b + b^2 = 4x^2 - 4xb + b^2.
By matching coefficients, in 4x212x+?4x^2 - 12x + \text{?}, we see 4xb=12x4xb = 12x. Thus, b=3b = 3.
Step 3: Substitute b=3b = 3 into b2b^2 to get the constant term: b2=32=9b^2 = 3^2 = 9.

Therefore, the solution to the problem is 3, 93,\text{ }9.

Answer

3, 9 3,\text{ }9

Exercise #15

Fill in the blanks:

(x?)2=x2?+25 (x-?)^2=x^2-?+25

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Recognize this as a binomial square problem.
  • Step 2: Identify the expanded form of a binomial square.
  • Step 3: Match the terms from both sides of the equation.

Now, let's work through each step:
Step 1: The given expression (x?)2=x2?+25(x-?)^2 = x^2 - ? + 25 is the expansion of a binomial (xa)2 (x-a)^2 .
Step 2: Recall that (xa)2=x22ax+a2(x-a)^2 = x^2 - 2ax + a^2.
Step 3: Compare this equivalent form to x2?+25x^2 - ? + 25:

- The term x2x^2 matches directly on both sides.
- The constant term a2=25a^2 = 25, so a=5a = 5 because 52=255^2 = 25.
- The middle term 2ax-2ax is currently unspecified, but it provides the form needed to fill the blank with 2ax-2ax.

Matching the expanded form: - The term inside (x?)(x-?) should be 55 (because a=5a=5).
- Therefore, the missing linear term can be 10x10x since 2×5=10-2 \times 5 = -10.

Therefore, the solution to the problem is 5, 10x5,\text{ }10x.

Answer

5, 10x 5,\text{ }10x