Question

(s+6)(s-15)=0

Answer 1

(s+6)(s-15)=0 ===> s=-6 or s=15

Answer 2

or if u want it like
\[s^2-15s+6s-90 = s^2-9-90\]

Answer 3

9s

Answer 4

If the propose is find s that satisfy the equation, you don't need multiply that sentences. Just think what is the value of s that cause 0 in each sentence. So, the values of s is -6 and 15, ok?

Answer 5

But, if the question is find the second grau equation, lalaly already done the work. ;)