Question

Mia is factoring the polynomial x2 + 4x – 12. She uses the steps shown. In which step did Mia make an error?

Answer 1

she make an error in the last step

Answer 2

While Mia's answer is not shown, the correct process is:

This trinomial is in the form ax²+bx+c.  In this case, x=1.  We want factors of c (in our trinomial, -12) that sum to b (in our trinomial, 4).  

To make -12, we can multiply:
1(-12)
-1(12)
2(-6)
-2(6)
3(-4)
-3(4)

The correct set of factors are the ones that sum to positive 4.  The only ones that do this are -2 and 6.  These are the roots, so factored form is:
(x-2)(x+6).