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x^2-2x>8

 Nov 19, 2018
 #1
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Re-arrange:

 

x^2-2x-8 >0   Factor

(x-4)(x+2) >0

 

For this to be true, BOTH o these terms must be > 0   or they must BOTH be less than 0

    x-4>0

    x > 4

 

and   x+2 >0

         x > -2             so the only answer interval that will work is   x >4  for both >0

 

 

x-4 <0     x < 4

 

x+2<0    x<-2           so the only answer here that will work is x <-2

   combined

                          -2> x > 4  

 Nov 19, 2018
edited by ElectricPavlov  Nov 19, 2018

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