math
posted by nice on .
What is the sum of all the possible values of a for which 25x^2+(a−15)x+9 has exactly one distinct real root?

To have one real root, the discriminant must be zero
(a15)^  4(25)(9) = 0
(a14)^2 = 900
a15 = ± 30
a = 15 ± 30
a = 45 or a = 15
so the sum of the a's = 4515 = 30