A rancher has a square cow pen with side length x. He deicdes to change the shape of the pen while still using

the same amount of fencing materials. The equation

(x + 10)(x - 10) = 300 represents the relationship

of the new side lengths (in feet) of the pen and its area

(in square feet).

a. If 300 represents the area of the new cow pen, what

do the expressions (r + 10) and (x - 10) each

represent?