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Of the five quadratics listed below, four of them have two distinct roots. The fifth quadratic has a repeated root. Find the value of the repeated root.
 

-x^2 + 18x + 81

 

3x^2 - 3x - 168

 

x^2 - 4x - 4 25

 

x^2 - 30x + 9 

 

x^2 - 14x + 24 

 Mar 19, 2020
 #1
avatar+1955 
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For this, we need to find a quadratic where you have to get a factored equation like (x+h)^2=0.

 

For this, you should factor all of these quadratics to look for the equation/expression that will get you (x+h)^2=0.

 Mar 19, 2020
 #2
avatar+111360 
+2

If we have a repeated root  the discriminant  will  =  0

 

Discriminant of first polynomial  = 18^2  - 4(-1)(81)   =   not zero

 

Discriminant of second polynomial    = (-3)^2 - 4(3) (-168) =  not zero

 

Discriminant  of  third polynomial  =  4^2 - 4(1)((-4.25)  = not zero

 

Discriminant of  fourth polynomial  = (-30)^2 - 4(1)(9)  =  not zero

 

Discriminant of fifth polynomial  =  (-14)^2  - 4(1)(24)  =  not zero

 

The first polynomial WOULD  have a repeated  root if we had  x^2 + 18x + 81   since  it can be factored as

 

(x + 9)^2

 

The repeated root  =  - 9

 

 

 

 

cool cool cool

 Mar 19, 2020
edited by CPhill  Mar 19, 2020
 #3
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Thx so much but i accidently posted something wrong in the problem so...

 Mar 19, 2020

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