Math

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Solve the following quadratic equation(as exact values) using the quadratic formula.

x^2-10x-15=0

I got 5+-2sqrt10/2.

^ Sorry hard to write it out. But basically there is a 5 there, the negative sign is supposed to be under the positive sign, then there is a two outside of the radicand, and inside the radicand is 10, all under 2.

  • Math -

    The answer is correct if it was meant to be, after cancelling the two's:
    5±√(10)

  • Math - correction -

    The answer is correct if it was meant to be (without the 2 in the denominator):
    5±2√(10)

  • Math -

    Where does that two in the denominator go? Since it has to cancel out with all terms.

  • Math -

    x=(-b±sqrt(b²-4ac))/2a
    a=1
    b=-10
    c=-15
    so substituting,
    x=(10±sqrt((-10)²-4(1)(-15)))/2
    =(10±sqrt(160))/2
    =(10±4sqrt(10))/2
    =5±2sqrt(10)

    You may have (like I did) subtracted 4ac (and got 40) instead of adding to get 160.

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