Q: If (6 - x)(6 + x) = -13, then what is a possible answer for x?
UNANSWERED.
The correct answer is D.
A:
One way to do this problem is to just plug in the possible answers and see which one fits the equation.
Let's try choice A, where x is 1, (6 - x)(6 + x) = -13 (6 - 1)(6 + 1) = -13 (5)(7) = -13 35 = -13 Nope, choice A doesn't work. Onto choice B, x is 3 ... (6 - x)(6 + x) = -13 (6 - 3)(6 + 3) = -13 (3)(9) = -13 27 = -13 Still not a match. Let's try choice C, where x is 5 ... (6 - x)(6 + x) = -13 (6 - 5)(6 + 5) = -13 (1)(11) = -13 11 = -13 Pft! Hope it's choice D, where x is 7 ... (6 - x)(6 + x) = -13 (6 - 7)(6 + 7) = -13 (-1)(13) = -13 -13 = -13 AT LAST, IT WORKS! So the answer is x is 7 or choice D.
Another way to solve it is algebraically: (6 - x)(6 + x) = -13 (x - 6)(x + 6) = 13 x2 - 36 = 13 x2 = 49 x = 7 or -7 So, D is the correct answer.
