Factor out the GCF of [tex]21x^3+24x^2-12x[/tex]
Take a look at the coefficients. Think about their prime factorization.
Each of these has 3 as a factor, so that can be taken out.
[tex]3(7x^3+8x^2-4x)[/tex]
Looking now at the variables, you might notice each has x as a factor.
Let's take that out.
We are left with our final answer [tex]\boxed{3x(7x^2+8x-4)}[/tex]
