Question 199238
we  can  use  (1) factoring , (2) graphing,  or  (3) quadratic  equation
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(1) x^2 -10x-39 =0
(x -13) ( x+3) =0
x= +13,  -3
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check  by  reinserting  in  original,,,13^2 -130 -39 = 169 -169 =0,,,ok
(-3)^2 -10(-3) -39 =  9 =30 -39 =0,,,ok
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(2)  using  graphing,  create  T  Box
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,,,,,,,,X,,,,,,,,,Y
,,,,,,,,,0,,,,,,,-39
,,,,,,,,-3,,,,,,,0,,,,,,,,,,x  intercept
,,,,,,,,13,,,,,,,0,,,,,,,,,,x  intercept
,,,,,,,,,,5,,,,,,,-64,,,,,,,vertex
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Plot  on  std  x / y coordinates  and  find  x=13, -3,,,,,as  zeroes
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(3)   use  quadratic  equation
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x  = [  -(b) +/- sqrt( (b)^2 - 4 (a) (c) )  ] / 2 (a)
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with  a = (1),,,b= (-10),,,,and c= (-39)
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x = [ -(-10) +/- sqrt  (-10)^2 - 4 (1) (-39) ] / 2 (1)
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x = [ 10 +/- sqrt( 100 + 156) ] /2  = 5 +/- 16/2 = +13,  -3