Examples with solutions for Extended Distributive Property: Solving the problem

Exercise #1

(2x+3)(2x3)=7 (2x+3)(2x-3)=7

Video Solution

Step-by-Step Solution

Let's solve the equation. First, we'll simplify the algebraic expressions using the abbreviated multiplication formula for difference of squares:

(a+b)(ab)=a2b2 (a+b)(a-b)=a^2-b^2

We will then apply the mentioned rule and open the parentheses in the expression in the equation:

(2x+3)(2x3)=7(2x)232=74x232=7 (2x+3)(2x-3)=7 \\ (2x)^2-3^2=7 \\ 4x^2-3^2=7

In the final stage, we distributed the exponent over the parentheses to both multiplication terms inside the parentheses, according to the laws of exponents:

(ab)n=anbn (ab)^n=a^nb^n

Let's continue and combine like terms, by moving terms:

4x232=7 4x29=74x216=0 4x^2-3^2=7 \ 4x^2-9=7 \\ 4x^2-16=0

Next - we can see that the equation is of second degree and that the coefficient of the first-degree term is 0, so we'll try to solve it using repeated use (in reverse) of the abbreviated multiplication formula for the difference of squares mentioned earlier:

4x216=0?a2b2(2x)242=0!a2b2(2x+4)(2x4)=0(a+b)(ab) 4x^2-16=0\stackrel{?}{\leftrightarrow } a^2-b^2\\ \downarrow\\ (2x)^2-4^2=0 \stackrel{!}{\leftrightarrow } a^2-b^2\\ \downarrow\\ \boxed{(2x+4)(2x-4)=0} \leftrightarrow (a+b)(a-b)\\

From here we'll remember that the product of expressions will yield 0 only if at least one of the multiplying expressions equals zero,

Therefore we get two simple equations and we'll solve them by isolating the unknown in each:

2x+4=02x=4/:2x=2 2x+4=0\\ 2x=-4\hspace{8pt}\text{/}:2\\ \boxed{x=-2}

or:

2x4=02x=4/:2x=2 2x-4=0\\ 2x=4\hspace{8pt}\text{/}:2\\ \boxed{x=2}

Let's summarize the solution to the equation:

(2x+3)(2x3)=7(2x)232=74x216=0(2x+4)(2x4)=02x+4=0x=22x4=0x=2x=2,2 (2x+3)(2x-3)=7 \\ \downarrow\\ (2x)^2-3^2=7 \\ 4x^2-16=0\\ \downarrow\\ (2x+4)(2x-4)=0\\ \downarrow\\ 2x+4=0\rightarrow\boxed{x=-2}\\ 2x-4=0\rightarrow\boxed{x=2}\\ \downarrow\\ \boxed{x=2,-2}

Therefore the correct answer is answer B.

Answer

x=±2 x=\pm2

Exercise #2

Solve for x:

(x+1)(2x+1)=2x2+4 (x+1)(2x+1)=2x^2+4

Video Solution

Step-by-Step Solution

Let's solve the equation, first we'll simplify the algebraic expressions using the extended distribution law:

(a+b)(c+d)=ac+ad+bc+bd (a+b)(c+d)=ac+ad+bc+bd We will therefore apply the mentioned law and open the parentheses in the expression in the equation:

(x+1)(2x+1)=2x2+42x2+x+2x+1=2x2+4 (x+1)(2x+1)=2x^2+4 \\ 2x^2+x+2x+1=2x^2+4 \\ We'll continue and combine like terms, by moving terms, then - we can notice that the term with the squared power cancels out and therefore it's a first-degree equation, which we'll solve by isolating the variable term on one side and dividing both sides of the equation by its coefficient:

2x2+x+2x+1=2x2+43x=3/:3x=1 2x^2+x+2x+1=2x^2+4\\ 3x=3\hspace{8pt}\text{/}:3\\ \boxed{x=1} Therefore, the correct answer is answer B.

Answer

x=1 x=1

Exercise #3

(x+1)(x+3)x=x2 (x+1)(x+3)-x=x^2

Video Solution

Step-by-Step Solution

Let's solve the equation, first we'll simplify the algebraic expressions using the extended distribution law:

(a+b)(c+d)=ac+ad+bc+bd (a+b)(c+d)=ac+ad+bc+bd We will therefore apply the mentioned law and open the parentheses in the expression in the equation:

(x+1)(x+3)x=x2x2+3x+x+3x=x2 (x+1)(x+3)-x=x^2 \\ x^2+3x+x+3 -x=x^2 \\ We'll continue and combine like terms, by moving terms, then - we can notice that the squared term cancels out and therefore it's a first-degree equation, which we'll solve by isolating the variable term on one side and dividing both sides of the equation by its coefficient:

x2+3x+x+3x=x23x=3/:3x=1 x^2+3x+x+3 -x=x^2\\ 3x=-3\hspace{8pt}\text{/}:3\\ \boxed{x=-1} Therefore, the correct answer is answer A.

Answer

x=1 x=-1