Algebra

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I've been trying to figure out this equation for over an hour but all the answers I get are wrong. The equation is 0.9=-10I^2+6I . The answer is supposed to be 0.3 and it does work out, but I have tried all different ways to solve for I and nothing seems to work. Could someone please help me?

  • Algebra -

    I assume you know how to complete the square
    -10 x^2 + 6 x = 0.9
    x^2 -.6 x = -0.09
    x^2 -.6 x + .09 = -.09+.09 = 0
    (x-.3)^2 = 0
    x = .3 sure enough.

  • Algebra -

    x^2 -.6 x = -0.09 or just rearrange and factor

    x^2 - .6 x + 0.09 = 0
    (x-.3)(x-.3) = 0
    x = .3 and x = .3

  • Algebra -

    oh, I forgot to thank you, so thank you very much!

  • Algebra -

    oh, that makes it so much easier! Thank you so very much, it all makes sense now! :D

  • Algebra -

    oh, okay, I see what you're doing. I just have one question, though;why is it that when you get rid of the -10, the 6 is affected by it? I would assume that it would be left alone...

  • Algebra -

    Or use quadratic equation
    -10 x^2 + 6 x = 0.9

    -10 x^2 + 6 x -.9 = 0
    a = -10
    b = 6
    c = -.9

    x = [-6 +/- sqrt (36-36) ]/-20
    =-6/-20
    =-3/-10
    = 0.3

  • Algebra -

    I divided both sides of the equation - ALL TERMS by -10

  • Algebra -

    -10 x^2 + 6 x
    ---------------
    -10

    = x^2 -.6 x

  • Algebra -

    oh, no wonder nothing worked out; thanks!

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