Question 285611
formula for area of a square is:


a = x^2


Increase the side by 8 cm and the formula becomes:


144 = (x+8)^2


You want to find the length of the side of the original square, which is x.


(x+8)^2 = x^2 + 16x + 64


Equation becomes:


144 = x^2 + 16x + 64


Subtract 144 from both sides of this equation to get


0 = x^2 + 16x - 80


This factors out to be:


0 = (x+20) * (x-4)


You get x = -20 or x = 4


x can't be negative so x has to be 4.


When x = 4, the area is 4^2 = 16
When x = 4 + 8 = 12, the area is 12^2 = 144


Numbers check out so answer is that the side of the original square is 4 cm.