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 The sum of an even number and its square is 240. What is the number?

 May 25, 2021
 #1
avatar+177 
+1

-16+256=240 so it is -16.

 May 25, 2021
 #2
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0

Not much of an explanation in your answers, ILP

 

x = number      x^2 = square of number

x^2 + x = 240

x^2 + x - 240 = 0

Use Quadratic formula with    a = 1    b=1    c = -240

\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)

 

and you will find  x = -16   or +15 (throw out...not even)

Check :  ( -16)^2 + -16 = 240        Check !

 May 25, 2021

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