What value of n makes this polynomial factorable by grouping?

Question

Given:

f(x)=4x^3 + 24x^2 + nx -42

Answer 1

In order to group, the ratio of the first two terms must equal the ratio of the last two terms.

So 4x³ / 24x² = nx / -42.

Simplifying gives:

x/6 = nx/-42

After solving for n, you get n = -7.

If you plug -7 back into the polynomial, you should see that you can factor by grouping