Exercise 39 Page 50

We want to write an expression for the perimeter of a rectangle whose area is represented by the equation below. A=x^2+13x-90We know that the area A can be calculated by multiplying the length by the width. Thus, x^2+13x-90 should be factored.

These factors represents the width and the length of the rectangle. Now, we can write an expression for the perimeter. The perimeter is twice the sum of the length and width. P=2(x-5+x+18) ⇔ P=4x+26