Solve: (x-1)(x+1)(x-2) = -2x²-x³ | Comparing Factored and Expanded Forms

Solve the following problem:

(x1)(x+1)(x2)=2x2x3 (x-1)(x+1)(x-2)=-2x^2-x^3

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Let's use shortened multiplication formulas to open the parentheses
00:15 Open parentheses properly
00:18 Each term multiplies each term
00:38 Collect terms and reduce what's possible
00:46 Isolate X
00:50 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

Solve the following problem:

(x1)(x+1)(x2)=2x2x3 (x-1)(x+1)(x-2)=-2x^2-x^3

2

Step-by-step solution

Solve the equation by simplifying the expression on the left side in two steps. First, we'll proceed to multiply the expressions in the two leftmost pairs of parentheses:

Apply the shortened multiplication formula for squaring a binomial:

(a±b)2=a2±2ab+b2 (a\pm b)^2=a^2\pm2ab+b^2

Due to the fact that these two pairs of parentheses are being multiplied by another expression (which is also in parentheses), place the result inside of parentheses (marked with an underline):

(x1)(x+1)(x2)=2x2+x3(x212)(x2)=2x2+x3(x21)(x2)=2x2+x3 \underline{ (x-1)(x+1)}(x-2)=-2x^2+x^3 \\ \underline{ (x^2-1^2)}(x-2)=-2x^2+x^3 \\ (x^2-1)(x-2)=-2x^2+x^3

Continue to simplify the expression on the left side by using the expanded distribution law:

(a+b)(c+d)=ac+ad+bc+bd (a+b)(c+d)=ac+ad+bc+bd

Additionally, apply the law of exponents for multiplying terms with equal bases:

aman=am+n a^ma^n=a^{m+n} We'll now apply these laws and expand the parentheses in the expression in the equation:

(x21)(x2)=2x2+x3x32x2x+2=2x2+x3 (x^2-1)(x-2)=-2x^2+x^3 \\ x^3-2x^2-x+2=-2x^2+x^3 \\ Continue to combine like terms, by moving terms between sides. Later - we can see that the terms with squared and cubed powers cancel out, 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:

x32x2x+2=2x2+x3x=2/:(1)x=2 x^3-2x^2-x+2=-2x^2+x^3\\ -x=-2\hspace{8pt}\text{/}:(-1)\\ \boxed{x=2}

Therefore, the correct answer is answer C.

3

Final Answer

x=2 x=2

Practice Quiz

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It is possible to use the distributive property to simplify the expression below?

What is its simplified form?

\( (ab)(c d) \)

\( \)

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