What is the value of c so that y=x^2+15x+c is a perfect square trinomial?
c must be 225/4 or 56.25
take 1/2 of 15, then square it
check:
(x + 15/2)^ = x^2 + 15x + 225/4
take 1/2 of 15, then square it
check:
(x + 15/2)^ = x^2 + 15x + 225/4