Solve x^2 - 9 = 0. What are the possible values of x?

Solve x^2 - 9 = 0. What are the possible values of x?

• A. x = 9 or x = -9
• B. x = 3 or x = -3
• C. x = 0 or x = 9
• D. x = 1 or x = -1

Answer: (B)

This equation is solved by recognizing a difference of squares. You can factor x^2 - 9 as (x - 3)(x + 3) = 0, and a product is zero when either factor is zero, giving x = 3 or x = -3. Another way is to move 9 to the other side to get x^2 = 9, then take square roots to obtain x = ±3. These two methods agree, confirming the solutions. The other options don’t satisfy the equation: substituting those values yields nonzero results (for example, x = 9 or -9 gives 72, x = 0 or 9 gives -9 or 72, and x = 1 or -1 gives -8).

This equation is solved by recognizing a difference of squares. You can factor x^2 - 9 as (x - 3)(x + 3) = 0, and a product is zero when either factor is zero, giving x = 3 or x = -3. Another way is to move 9 to the other side to get x^2 = 9, then take square roots to obtain x = ±3. These two methods agree, confirming the solutions. The other options don’t satisfy the equation: substituting those values yields nonzero results (for example, x = 9 or -9 gives 72, x = 0 or 9 gives -9 or 72, and x = 1 or -1 gives -8).