Question

factor completely.
4a^3-28a^2-8a

Answer 1

The easiest thing to do first is to take out the greatest common factor:

\[4a(a^2-7a-2)\]
Next you want to focus on the trinomial in the brackets. What are two numbers that multiply to give -2 and add to give -7? There aren't any. Even if you try using the quadratic formula, you'll find that your solutions aren't real numbers. That means the trinomial can't be factored any more, and what's written above is the fully factored form of your original expression!