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how you do this

ISmellGood  Oct 20, 2017
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 #1
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We have that

 

(-3)^2 + m(-3) + n  = 0

 

9  - 3m + n  = 0      →     n =   3m - 9       (1)

 

If x = -3 is the only possible solution...we only have one root...so......the discriminant must  = 0

 

So

 

m^2  -  4n  = 0     sub (1)  into this

 

m^2 - 4 [ 3m - 9 ]  = 0   simplify

 

m^2 - 12m + 36  =  0       factor

 

(m - 6)^2  = 0

 

Which implies that  m  = 6

 

And n  = 3(6) - 9  = 9

 

So....our function is   x^2 + 6x + 9 = 0

Check to see that  x = -3  is the only root

 

 

cool cool cool

CPhill  Oct 20, 2017

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