If 4x^2+20x+r=(2x+s)^2 for all values of x, what is the value of r-s?

Question

Can you please help me?

Answer 1

just expand and equate coefficients

4x^2+20x+r = 4x^2+4sx+s^2

4s=20
s=5

r = s^2 = 25

r-s = 20