Factor by grouping.
-$5 x ^ { 3 } - 15 x ^ { 2 } - 4 x + 12$
A) $\left( 5 x ^ { 2 } - 4 \right) ( x + 3 )$
B) $\left( 5 x ^ { 2 } - 4 \right) ( x - 3 )$
C) $\left( 5 x ^ { 2 } + 4 \right) ( x - 3 )$
D) $\left( 5 x ^ { 2 } + 4 \right) ( x + 3 )$

Question

Quizplus · Accepted Answer

First, group the first two terms and the last two terms:

\begin{align*}
5x^3 - 15x^2 - 4x + 12 &= (5x^3 - 15x^2) - (4x - 12) \
&= 5x^2(x-3) - 4(x-3) \
&= (5x^2-4)(x-3)
\end{align*}

Therefore, the answer is B.

Factor by Grouping 5x3−15x2−4x+125 x ^ { 3 } - 15 x ^ { 2 } - 4 x + 125x3−15x2−4x+12

Factor by Grouping $5 x ^ { 3 } - 15 x ^ { 2 } - 4 x + 12$