SAT Mathematics Practice Test 7

Since x = −3 is a solution to the equation, substituting −3 for x gives${\left(-3\mathit{a}+3\right)}^2=36$. Taking the square root of each side of this equation gives the two equations −3a + 3 = 6 and −3a + 3 = −6. Solving each of these for a yields a = −1 and a = 3. Therefore, −1 is a possible value of a.