A rectangle has sides... find the remaining area

Question

A rectangle has sides (x+3)ft and (x+5)ft. If a square x ft on a side is cut from the rectangle, represent the remaining area in terms of x. 

Answer 1

The area of the rectangle is (x + 3)*(x + 5) = (x² + 8x + 15) square feet.

 

The side of the square is x and the square has an area of x² square feet

 

Subtract the area of the square from the area of the rectangle:

(x2 + 8x + 15) - x2 = 8x + 15 square feet. 

 

This is the remaining area of the rectangle.