Squares

 

If each side of a square were increased by seven feet the area would be three hundred fifteen square larger. What is the length of a side 

 

Call the side of the square X  

 

Then                                          (X + 7)²  =  X² + 315  

 

Multiply out the left side            X² + 14X + 49  =  X² + 315  

 

Subtract X² from both sides        14X + 49  =  315 

 

Subtract 49 from both sides          14X  =  266    

 

Divide both sides by 14                     X  =  19   

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