Question

When asked to factor the trinomial x^2 - 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 plus sign should be a minus sign.

C. The answer is incorrect; the minus sign should be a plus sign.

D. The answer is correct.

Answer 1

B.The answer is incorrect; the plus sign should be a minus sign.

Explanation:

`x^2-18x+81\\\\=x^2-2\cdot 9x +9^2\\\\=(x-9)^2\\\\=(x-9)(x-9)`