SOLUTION: If the sides of a square are decreased by 3 cm, the area is decreased by 81 cm2. What were the dimensions of the original square? L - 3 x W - 3 = -81cm2 +3 +3 = +6 L x

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Question 103809: If the sides of a square are decreased by 3 cm, the area is decreased by 81 cm2. What were the dimensions of the original square?
L - 3 x W - 3 = -81cm2
+3 +3 = +6
L x W = -75cm2
/2 = /2
L x W = -37.5
Can someone help me, I keep messing up the formula, please help
Answer by kev82(151) About Me  (Show Source):
You can put this solution on YOUR website!
Firstly, it is a square, so L=W. I'm going to call this length X. The area of it now is X%5E2, But if we decrease the side lengths it becomes 81 units smaller so the decreased area is X%5E2-81.
Both of the dimensions have been decreased by 3 units, so the area after the decrease can also be worked out as %28X-3%29%28X-3%29.

Both of these expressions gives the same thing (the area after the decrease) so they must be equal, hence:

%28X-3%29%28X-3%29=X%5E2-81

See if you ca solve this equation for X.

Kev