Consider the expression [tex]6x^3-864x.[/tex] This expression consists of two terms: [tex]6x^3[/tex] and [tex]-864x.[/tex]
These two terms have common factors 6 and x, because:
- [tex]6x^3=6x\cdot x^2;[/tex]
- [tex]-864x=6x\cdot (-144).[/tex]
Then
[tex]6x^3-864x=6x(x^2-144).[/tex]
You know that [tex]144=12^2.[/tex] Use the formula for the difference of squares:
[tex]x^2-144=x^2-12^2=(x-12)(x+12).[/tex]
Therefore,
[tex]6x^3-864=6x(x-12)(x+12).[/tex]
Answer: correct choice is C.
