#1**+1 **

The area of a rectangle is the length times the width. The length is (2+x) and the width is (3+x). So the area of ABCD is...

(2+x)(3+x).

Using the FOIL method of multiplying binomials, we get...

(2+x)(3+x)=x^2+5x+6

as the area of ABCD. However, the problem states that the area of ABCD is 9. Since both 9 and x^2+5x+6 are the area of ABCD, we can set them equal to each other.

x^2+5x+6=9

Then, just subtract 6 from both sides, and you get...

x^2+5x=3

which is the equation we were trying to get.

Guest Jun 10, 2018