Question

What value, in place of the question mark, makes the polynomial below a perfect square trinomial?x2 - 28x + ?

Answer 1

to make a square, when a=1, add {(1/2) of b}²
in this case, a=1, b=-28, half of -28 is -14, (-14) squared is 196
x²-28x+196=(x-14)²

the ? is 196