Answer:
l = 12
Step-by-step explanation:
Let l = length
width = l+9
The area of rectangle is
A = lw
A = l * (l+9)
252 = l^2 +9l
Subtract 252 from each side
0 = l^2 +9l -252
Factor
What 2 numbers multiply to -252 and add to 9
21*-12 = 252
21-12 = 9
0 = (l+21) (l-12)
Using the zero product property
l+21=0 l-12=0
l = -21 l = 12
We cannot have a negative length
l = 12
