Question

Factor the expression by taking out the GCF. 3x - 9x3

A. x(3 - 9x2)

B. 3x(1 - 3x2)

C.3(x - 3x3)

D. none of the above

Answer 1

Consider the expression $3x-9x^3.$ It consists of two terms:

$3x=3\cdot x$

and

$-9x^3=-3\cdot 3\cdot x\cdot x\cdot x.$

The common factors in these terms are $3$ and $x.$ Then

$GCF(3x,-9x^3)=3x.$

Taking out the GCF, you obtain

$3x-9x^3=3x(1-3x^2).$

Answer: correct choice is B.