Question

When asked to factor the trinomial x2 - 18x + 81, a student gives the answer (x - 9)(x + 9). Which of the following statements is true?

A. The answer is incorrect; the trinomial cannot be factored.
B. The answer is incorrect; the minus sign should be a plus sign.
C. The answer is incorrect; the plus sign should be a minus sign.
D. The answer is correct.

Answer 1

The answer is C. (X-9)(x+9) equals x^2 -81. But, (x-9)(x-9) is x^2-18x+81.