Question

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Answer 1

1) x^2 - 169 = 0
    x^2 = 169
x = Sqrt(169)  
x = +-  13
2) x^2 + x - 42 = 0
D = 1^2 - 4*1*(-42) = 1+ 168 = 169  ;  Sqrt(D) = Sqrt(169) = 13
x' = (-1 + 13)/2*1 = 12/2 = 6  ;  x" = (- 1 - 13)/2*1 = -14 / 2 = -7
3) 12x^2 + 16x -3 = 0
D = 16^2 - 4*12*(-3) = 256 + 144 = 400 ;  Sqrt(400) = 20
x' = (-16 + 20)/2*12 = 4/24 = 1/6  ; 
x" = (-16 - 20) / 2*12 = - 36/24 =  - 3/2 = - 1 1/2