Question

Teslim is designing a cover for a book. He wants to have a rectangular grid with x2 – 10x + 21 squares in it, for some positive whole number x. What are the possible side lengths for the grid? A. (x – 3) and (x – 7) B. (x – 3) and (x + 7) C. There are no possible whole number side lengths. D. (x + 3) and (x + 7)

Answer 1

A. (x – 3) and (x – 7)

Explanation:

A. (x – 3) and (x – 7) = x^2 - 10x + 21

x*x = x^2
x*-7 = -7x

-3*x = -3x

-3*-7 = 21

x^2 - 7x + 3x + 21

x^2 - 10x + 21