SOLUTION: If the sides of a square are decreased by 3 cm, the area is decreased by 81 cm^2. What were the dimensions of the original square? Thank you.

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: If the sides of a square are decreased by 3 cm, the area is decreased by 81 cm^2. What were the dimensions of the original square? Thank you.      Log On


   

Question 76596: If the sides of a square are decreased by 3 cm, the area is decreased by 81 cm^2. What were the dimensions of the original square?
Thank you.
Answer by checkley75(3666) About Me  (Show Source):
You can put this solution on YOUR website!
(x-3)(x-3)=x^2-81
x^2-6x+9=x^2-81 the x^2 factors cancel out thus:
-6x=-81-9
-6x=-90
x=-90/-6
x=15 cm. the original length of the sides of the square.
proof
(15-3)(15-3)=12^2-81
12*12=15^2-81
144=225-81
144=144