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Math Help - Rearranging a quadratic equation

  1. #1
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    Rearranging a quadratic equation

    y=(4-x)(2+x)

    Can this be rearranged to make an equation x=something without x being on the rhs?
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  2. #2
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    Quote Originally Posted by Stuck Man View Post
    y=(4-x)(2+x)

    without x being on the rhs?
    y=(4-x)(2+x)

    y=8+4x-2x-x^2

    y=8-2x-x^2

    x^2+2x+y=8
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  3. #3
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    I want the lhs to be x.
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  4. #4
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    hmm

    x(x+2) = 8-y
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  5. #5
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    No the lhs has to be x alone. I don't think it can be done.
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  6. #6
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    Exclamation right

    Quote Originally Posted by Stuck Man View Post
    No the lhs has to be x alone. I don't think it can be done.
    if it has to be x alone i am sure it cant be done
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  7. #7
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    Cool yess

    amul's answer is the best and simple answer
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  8. #8
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    x= sqrt(9-y)+1

    I moved the graph left by 1 to have the axis of symmetry at the y-axis. Then I rearranged it and added 1.

    y=-x^2+9
    x=sqrt(9-y)
    add 1
    x=sqrt(9-y)+1
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  9. #9
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by Stuck Man View Post
    y=(4-x)(2+x)

    Can this be rearranged to make an equation x=something without x being on the rhs?
    y = 8+2x-x^2

    x^2-2x+8-y = 0

    You can use the quadratic formula to find x

    x = 1 \pm \sqrt{y-7}
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  10. #10
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    Quote Originally Posted by e^(i*pi) View Post
    y = 8+2x-x^2

    x^2-2x+8-y = 0

    You can use the quadratic formula to find x

    x = 1 \pm \sqrt{y-7}
    ya this can b done...
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  11. #11
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    There are two signs wrong after rearranging.

    After using the quadratic formula I have come up with a different but equivalent equation to my earlier one.

    I can also make it equal to my earlier equation using some interesting algebra that I've thought of.
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  12. #12
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    Quote Originally Posted by Stuck Man View Post
    There are two signs wrong after rearranging.

    After using the quadratic formula I have come up with a different but equivalent equation to my earlier one.

    I can also make it equal to my earlier equation using some interesting algebra that I've thought of.
    i guess the bfore eq was a bit complex....maybe fr me
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  13. #13
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    I've attached a scan of my work. I was planning to do integration against the y-axis but it happens to be more work.
    Attached Thumbnails Attached Thumbnails Rearranging a quadratic equation-scan-1.jpg  
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