GMAT Practice Question: If x is not equal to -\frac{1}{2}, then \frac{6x^3+3 x^2-8x-4}{2x+1}=
Question
If x is not equal to -\frac{1}{2}, then \frac{6x^3+3 x^2-8x-4}{2x+1}=
- 3 x^{2}+\frac{3}{2} x-8
- 3 x^{2}+\frac{3}{2} x-4
- 3 x^{2}-4
- 3 x-4
- 3 x+4
Topics: factoring, equations with unknowns in the denominator
Solution
Step 1
We group the numerator into two pairs to set up factoring.
6x^3 + 3x^2 - 8x - 4 = 3x^2(2x+1) - 4(2x+1)
Step 2
We factor out the common binomial from each group.
3x^2(2x+1) - 4(2x+1) = (2x+1)(3x^2 - 4)
Step 3
We remove the common factor since 2x+1 is nonzero under the given condition.
\frac{\cancel{(2x+1)}(3x^2 - 4)}{\cancel{(2x+1)}} = 3x^2 - 4
Answer
3x^2 - 4
