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Complete the square to obtain exact solutions:

x^2+6x+13 = 0

2x^2-5x-3 = 0

  • Algebra -

    In the first problem, you want to have
    x^2 + 6x + 9 on the left side, since that is the perfect square (x+3)^2.
    You can make that happen by rewriting the equation as
    (x+3)^2 = -4
    x +3 = + or- 2i
    x = -3 +/- 2i

    (i is the square root of -1)

    Now that you have seen how completing the square works, you should try the second one. I would factor out 2 first to make the perfect square simpler. Start with

    x^2 -(5/2)x = 3/2 (a)

    The perfect square that you need is
    x -(5/2)x + 25/16 = [x -(5/4)]^2
    So add 25/16 to both sides of Equation (a)and go from there.

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