X^2+20x+c What is the value of c such that is a perfect -square trionomial?

Answer 1

This is called "completing the square".

Lauren gave you the correct answer; This will help you understand how she did it.

A generic perfect square (x+a)² = x² + ax + ax + a² = x² + 2ax + a²

The last number is the square of half of the center coefficient. (Half of 2a is a)

For this problem, that means that we need the square of half of 20. That's 10².= 100.

Answer 2

X^2+20x+c

(x + 10) (x + 10) = x^2 + 20x + 100

c = 100