Question

The length of a rectangle is 4 less than twice the width. The area of the rectangle is 70 square feet. Find the width, w, of the rectangle algebraically. Explain why one of the solutions for w is not viable.

Answer 1

Area = Length * Width
Length = 2w - 4
Width = w

70 = (2w - 4)w
70 = 2w² - 4w
2w² - 4w - 70 = 0
2(w² - 2w - 35) = 0
2(w + 5) (w - 7) = 0
w + 5 = 0 ; w -7 = 0
w = -5 ; w = 7

w = -5 is not viable because no length of measurement is negative.