Consider the expression [tex]3x-9x^3.[/tex] It consists of two terms:
[tex]3x=3\cdot x[/tex]
and
[tex]-9x^3=-3\cdot 3\cdot x\cdot x\cdot x.[/tex]
The common factors in these terms are [tex]3[/tex] and [tex]x.[/tex] Then
[tex]GCF(3x,-9x^3)=3x.[/tex]
Taking out the GCF, you obtain
[tex]3x-9x^3=3x(1-3x^2).[/tex]
Answer: correct choice is B.
