Question

What is the value of c such that: x2 + 14x + c, is a perfect-square trinomial?

Answer 1

Take 1/2 of the coefficient of x, and square the number.

The coefficient of the x term is 14.

So 1/2 of 14 is 7. And 7^2 = 49.

c = 49

Answer 2

KK Thanks.

Answer 3

And it checks, because if c = 49
you have

x^2 + 14x + 49 = (x+7)(x+7) or (x+7)^2
which is a perfect square trinomial.