Solution:
[tex]3x^3-9x^2-12x[/tex]Step 1:
Factor out the common term
The common term is 3x
By doing this, we will have
[tex]\begin{gathered} 3x^3-9x^2-12x=3x(\frac{3x^3}{3x}-\frac{9x^2}{3x}-\frac{12x}{3x}) \\ =3x(x^2-3x-4) \end{gathered}[/tex]Step 2:
Factorise the quadratic expression in the bracket
[tex]3x(x^2-3x-4)[/tex]By doing this, we will have to look for two factors to multiply to give i4 and if we add them together, we will have -3
The two factors are -4 and +1
therefore,
Replace -3x with -4x + x
[tex]\begin{gathered} 3x(x^2-3x-4) \\ =3x(x^2-4x_{}+x-4) \\ =3x(x(x-4)+1(x-4) \\ =3x(x+1)(x-4) \end{gathered}[/tex]Hence,
The final answer is = (x-4)
