SAT Math Question of the Day

Q: If (x + 4)(x - 4) = 9, then what is a possible answer for x?

1. -5
2. -3
3. -1
4. 1
5. 3

UNANSWERED.

The correct answer is A.

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 -5, first:
(x + 4)(x - 4) = 9
(-5 + 4)(-5 - 4) = 9
(-1)(-9) = 9
9 = 9
IT WORKS!
So the answer is x is -5 or choice A.

Another way to solve it is algebraically:
(x + 4)(x - 4) = 9
x² - 16 = 9
x² = 25
x = 5 or -5
So, A is the correct answer.