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  • Solve | x2– 4x – 5 | = 7

 Aug 14, 2015

Best Answer 

 #1
avatar+130462 
+5

l x^2 - 4x - 5 l   = 7    we have two equations here......

 

The first is :

 

x^2 - 4x - 5  = 7    subtract 7 from both sides

 

x^2 - 4x - 12 = 0    factor

 

(x - 6) ( x + 2)  = 0      and, setting each linear factor  to  0   means that  x= 6 or x = -2

 

The second equation is :

 

-(x^2 - 4x  - 5)  = 7       multiply both sides by -1

 

x^2 - 4x - 5  = -7      add 7 to both sides

 

x^2 - 4x + 2  = 0     the solution to this is:

 

x24×x+2=0{x=22x=2+2}{x=0.585786437626905x=3.414213562373095}

 

Thus...we have 4 values that make this true....

 

  

 Aug 14, 2015
 #1
avatar+130462 
+5
Best Answer

l x^2 - 4x - 5 l   = 7    we have two equations here......

 

The first is :

 

x^2 - 4x - 5  = 7    subtract 7 from both sides

 

x^2 - 4x - 12 = 0    factor

 

(x - 6) ( x + 2)  = 0      and, setting each linear factor  to  0   means that  x= 6 or x = -2

 

The second equation is :

 

-(x^2 - 4x  - 5)  = 7       multiply both sides by -1

 

x^2 - 4x - 5  = -7      add 7 to both sides

 

x^2 - 4x + 2  = 0     the solution to this is:

 

x24×x+2=0{x=22x=2+2}{x=0.585786437626905x=3.414213562373095}

 

Thus...we have 4 values that make this true....

 

  

CPhill Aug 14, 2015

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