Question

The length of a rectangle is 5 inches more than twice a number.The width is 4 inches less than the same number.If the area of the rectangle is 15,find the number.

Answer 1

n = 5, n = -7/2

Explanation:

2n + 5 = l

n - 4 = w

A = l × w = 15

(2n + 5)(n-4) = 15

2n^2 - 8n + 5n - 20 = 15

2n^2 -3n - 35 = 0

(2n + 7)(n - 5) = 0

2n + 7 = 0 or n - 5 = 0

n = -7/2 or n = 5