How do you get the real-number solutions of 5b^3 + 15b^2 + 12b = -36?

Question

I get to (b+3)(5b^2 + 12) and I don't know what to do after that. Can someone please show me how to finish this problem?

Answer 1

5b^3 + 15b^2 + 12b = -36
5b^3 + 15b^2 + 12b +36 = 0
you factored it correctly to

(b+3)(5b^2 + 12) = 0
that was the hard part, the rest is easy

so b+3 = 0 or b = -3
or
5b^2 + 12 = 0

b^2 = -12/5 ---> no real solution

so the only real solution is b = -3

Answer 2

Thank you :-)

Answer 3

oops wrong question.