Question

Using the quadratic formula, find the solution to x^2+6x+9=0

Answer 1

For ax^2+bx+c with a=1, b=6, c=9 the quadratic formula gives
x = [-b ± sqrt(b^2−4ac)]/(2a) = [-6 ± sqrt(36−36)]/2 = [-6 ± 0]/2 = -3.

So the equation has a repeated root x = -3 (indeed x^2+6x+9 = (x+3)^2).