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The expression $x^2 + 3x - 28$ can be written as $(x + a)(x - b),$ and the expression $x^2 - 10x - 56$ written as $(x + 2b)(x + c)$, where $a$, $b$, and $c$ are integers such that $c > 0.$ What is the value of $2c - a$?

 Mar 19, 2020
 #1
avatar+111360 
+1

x^2  + 3x - 28  =    ( x  + (-4) )  (  x - ( - 7 ) )             a   = -4     b  = -7

 

x^2 - 10x - 56  =   (x - 14 ) ( x + 4)  =  ( x + 2(-7) )  ( x + 4)       c  = 4

 

So

 

2c - a   =

 

2(4) - (-4)  =

 

8  + 4   =

 

12

 

cool cool cool

 Mar 19, 2020

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