How to solve this quadratic equation with the quadratic formula? Help?

Question

Could someone help me with this question step-by-step using the quadratic formula?

3x² + 24x – 144

Answer 1

3x^2+24x-144

factor out a 3

3(x^2+8x-48)

factor

3(x+12)(x-4)

 

but you want to use the quadratic formula

 

(-8±√[64+192])/2

(-8±√256)/2

(-8±16)/2

-24/2 and 8/2

-12 and 4

don't forget the 3 you factored out !!!

3(x+12)(x-4)