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A rectangle has length (x + 5)cm and width (x –2)cm. Its area is 60 cm^2.  What is x?

 Feb 21, 2021
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A rectangle has length (x + 5)cm and width (x –2)cm. Its area is 60 cm^2.  What is x?    

 

Length times Width equals Area.  So,                     (x + 5)(x – 2) = 60  

 

Multiply it out and subtract 60 from both sides        x2 + 3x – 10 – 60  =  0  

                                                                                x2 + 3x – 70  =  0 

 

Factor it                                                                  (x + 10)(x – 7)  =  0

 

                                                                                 x = –10  and  x = 7  

 

You can't have a negative side so discard that one which leaves  x = 7   

.

 Feb 21, 2021

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