lucy5761 lucy5761
  • 03-10-2019
  • Mathematics
contestada

solve 3x^2=-12x-15
x=-4+2i
x=-4+i
x=-2+2i
x=-2+i

Respuesta :

zrh2sfo
zrh2sfo zrh2sfo
  • 03-10-2019

Answer:

x = -2 + i or x = -2 - i

Step-by-step explanation:

Solve for x:

3 x^2 = -12 x - 15

Add 12 x + 15 to both sides:

3 x^2 + 12 x + 15 = 0

Divide both sides by 3:

x^2 + 4 x + 5 = 0

Subtract 5 from both sides:

x^2 + 4 x = -5

Add 4 to both sides:

x^2 + 4 x + 4 = -1

Write the left hand side as a square:

(x + 2)^2 = -1

Take the square root of both sides:

x + 2 = i or x + 2 = -i

Subtract 2 from both sides:

x = -2 + i or x + 2 = -i

Subtract 2 from both sides:

Answer: x = -2 + i or x = -2 - i

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