chyna13 chyna13
  • 08-01-2017
  • Mathematics
contestada

X^2+6x+90=0
A)x=-3+9i, -3-9i
B)x=-12
C)x=6,-12
D)x=-3+9i

Respuesta :

thehuylui
thehuylui thehuylui
  • 08-01-2017
First, we con solve the quadratic by completing the squares
x^2 + 6x + 90 = 0
x^2 + 6x = -90
x^2 + 6x + 9 = -81   (to complete the square, half teh b calue squared gives us the c value)
(x + 3)^2 = -81
x +3 = +√(-81) and -√-81
x + 3= 9i and -9i
x = -3 + 9i and -3 - 9i
Choice A is correct
Answer Link

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