Solve the Quadratic Equation: Finding X in 3x²-3x=6

Quadratic Equations with Factoring Methods

3x23x=6 3x^2-3x=6

Determine the value of X:

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Arrange the equation so the right side equals 0
00:13 Divide to reduce the trinomial coefficients
00:28 Pay attention to the trinomial coefficients
00:32 We want to find 2 numbers
00:43 Their sum equals B and their product equals C
00:47 These are the matching numbers
00:51 Therefore these are the numbers we'll put in parentheses
00:56 Find the solutions that zero each factor
01:00 Isolate X, this is one solution
01:08 Isolate X, this is the second solution
01:17 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

3x23x=6 3x^2-3x=6

Determine the value of X:

2

Step-by-step solution

Solve the given equation:

3x23x=6 3x^2-3x=6

First, let's organize the equation by moving and combining like terms:

3x23x=63x23x6=0 3x^2-3x=6 \\ 3x^2-3x-6=0 \\ Note that all coefficients and the free term are multiples of 3, hence we'll divide both sides of the equation by 3:

3x23x6=0/:3x2x2=0 3x^2-3x-6=0 \hspace{6pt}\text{/}:3 \\ x^2-x-2=0

Note that the coefficient of the squared term is 1, therefore, we can (try to) factor the expression on the left side using quick trinomial factoring:

Let's look for a pair of numbers whose product equals the free term in the expression, and whose sum equals the coefficient of the first-degree term, meaning two numbers m,n m,\hspace{2pt}n that satisfy those values:

mn=2m+n=1 m\cdot n=-2\\ m+n=-1\\ From the first requirement mentioned, that is - from the multiplication, we notice that the product of the numbers we're looking for needs to be negative. Therefore we can conclude that the two numbers have different signs, according to multiplication rules. Remember that the possible factors of 2 are 2 and 1, satisfying the second requirement mentioned. This along with the fact that the numbers we're looking for have different signs leads us to the conclusion that the only possibility for the two numbers we're looking for is:

{m=2n=1 \begin{cases} m=-2 \\ n=1 \end{cases}

Therefore we'll factor the expression on the left side of the equation to:

x2x2=0(x2)(x+1)=0 x^2-x-2=0 \\ \downarrow\\ (x-2)(x+1)=0

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

Therefore we obtain two simple equations which we solve by isolating the unknown in each:

x2=0x=2 x-2=0\\ \boxed{x=2}

or:

x+1=0x=1 x+1=0\\ \boxed{x=-1}

Let's summarize the solution of the equation:

3x23x=63x23x6=0x2x2=0(x2)(x+1)=0x2=0x=2x+1=0x=1x=2,1 3x^2-3x=6 \\ 3x^2-3x-6=0 \\ x^2-x-2=0 \\ \downarrow\\ (x-2)(x+1)=0 \\ \downarrow\\ x-2=0\rightarrow\boxed{x=2}\\ x+1=0\rightarrow\boxed{x=-1}\\ \downarrow\\ \boxed{x=2,-1}

Therefore the correct answer is answer B.

3

Final Answer

x1=2,x2=1 x_1=2,x_2=-1

Key Points to Remember

Essential concepts to master this topic
  • Standard Form: Move all terms to one side: ax² + bx + c = 0
  • Factoring: Find two numbers that multiply to c and add to b
  • Check: Substitute both solutions back: 3(2)²-3(2)=6 and 3(-1)²-3(-1)=6 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to move all terms to one side
    Don't try to factor 3x²-3x=6 directly = impossible to factor! The equation must equal zero for factoring to work. Always rearrange to standard form ax²+bx+c=0 first.

Practice Quiz

Test your knowledge with interactive questions

\( x^2+6x+9=0 \)

What is the value of X?

FAQ

Everything you need to know about this question

Why do I need to get everything on one side first?

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Factoring only works when the equation equals zero. This is because we use the zero product property: if (x-a)(x-b)=0, then either x-a=0 or x-b=0.

How do I find the two numbers for factoring?

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Look for two numbers that multiply to give the constant term and add to give the coefficient of x. For x²-x-2=0, we need numbers that multiply to -2 and add to -1: that's -2 and +1!

What if I can't factor the quadratic?

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Not all quadratics can be factored easily! If factoring doesn't work, you can use the quadratic formula or completing the square methods instead.

Why are there two answers to a quadratic equation?

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A quadratic equation represents a parabola, which can cross the x-axis at two points. Each crossing point gives us a solution to the equation.

How do I check if my answers are correct?

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Substitute each solution back into the original equation. For x=2: 3(2)23(2)=126=6 3(2)^2-3(2)=12-6=6 ✓. For x=-1: 3(1)23(1)=3+3=6 3(-1)^2-3(-1)=3+3=6

Can I divide by 3 first to make it simpler?

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Yes! Always look for common factors first. Dividing 3x23x6=0 3x^2-3x-6=0 by 3 gives us x2x2=0 x^2-x-2=0 , which is much easier to factor.

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