For what real values of s is 9x^2 + sx + 4 the square of a binomial?
9x^2 + sx + 4
Take the positive root of 9x^2 and both roots of 4 = 3x and +/- 2
(3x + 2)^2 =
9x^2 + 12x + 4
s = 12
Also
(3x -2)^2 =
9x^2 - 12x + 4
s = -12
