GMAT Quantitative Practice, Problem Solving
If x2 + 6x = –9, how many values of x are possible?
- infinitely many
First, restate the equation in standard quadratic form:
x2 + 6x + 9 = 0The trinomial on the left side of the equation is factorable into two identical binomials:
(x + 3)(x + 3) = 0
To find the roots, set each binomial factor equal to zero. Since the two factors are the same, the equation has only one root: –3. The correct response is (B).