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7 November, 19:54

Solve 3x^2=-12x-15

x=-4+2i

x=-4+i

x=-2+2i

x=-2+i

+4
Answers (1)
  1. 7 November, 20:11
    0
    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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