Question

What value of c makes x2 − 24x + c a perfect square trinomial?

−144
−48
48
144

Answer 1

We want x^2 − 24x + c to equal (x − a)^2 = x^2 − 2ax + a^2. So −2a = −24 ⇒ a = 12, and c = a^2 = 144.