SOLUTION: If the sides of a square are lengthened by 5cm, the area becomes 81cm^2. Find the length of a side of the original square.

Question 157114: If the sides of a square are lengthened by 5cm, the area becomes 81cm^2. Find the length of a side of the original square.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
If the sides of a square are lengthened by 5cm, the area becomes 81cm^2.
Find the length of a side of the original square.
:
let x = side of original square
then
(x+5) = side of the new square
and
(x+5)^2 = area of the new square
:
The problems states:
(x+5)^2 = 81
FOIL
x^2 + 10x + 25 = 81
:
x^2 + 10x + 25 - 81 = 0
:
x^2 + 10x - 56 = 0; a quadratic equation
Factors to:
(x+14)(x-4) = 0
Positive solution
x = +4 is the side of the original square
:
:
Check solution: New square side; 4 + 5 which has an area of 81 sq/cm
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