Q: If (a + 2)(a - 2) = 12, then what is a possible value for a?
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 a is -10, (a + 2)(a - 2) = 12 (-10 + 2)(-10 - 2) = 12 (-8)(-12) = 12 96 = 12 Nope, choice A doesn't work. On to choice B: a is -8 ... (a + 2)(a - 2) = 12 (-8 + 2)(-8 - 2) = 12 (-6)(-10) = 12 60 = 12 That didn't work. Let's try choice C: a is -6 ... (a + 2)(a - 2) = 12 (-6 + 2)(-6 - 2) = 12 (-4)(-8) = 12 32 = 12 Maybe choice D, where a is -4 will work (a + 2)(a - 2) = 12 (-4 + 2)(-4 - 2) = 12 (-2)(-6) = 12 12 = 12 HOORAY, IT WORKS! So the answer is a is -4 or choice D.
Another way to solve it is algebraically: (a + 2)(a - 2) = 12 a2 - 4 = 12 a2 = 16 a = 4 or -4 So, D is the correct answer.
