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.