100p-5p^2 = 0
Factor out 5p out of 100p and -5p^2:
5p(20) + 5p(-p) = 0
Factor:
5p(20-p)=0
Divide each term by 5:
p = 0
Set 20-p to 0 and solve for p:
p = 20
The answer is 0, 20