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Math Help - positive exponents

  1. #1
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    positive exponents

    Write with only positive exponents.


    (3x^2 y) (-2x^-2 y)


    I got -6x^2 y^2

    But the teacher got -6y^2

    I don't understand how he got that
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  2. #2
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    Re: positive exponents

    Quote Originally Posted by Candy101 View Post
    Write with only positive exponents.
    (3x^2 y) (-2x^-2 y)
    (3x^2 y) (-2x^{-2} y)=(3)(-2)(x^{2-2})(y^{1+1})=-6y^2
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  3. #3
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    Re: positive exponents

    Oh I see Wht I did wrong. I forgot about the x^-2 . Which cancels out!


    Thanks


    (2x^-2 y)^3 / -2x^-2 y^-3

    For this one I can't understand why he got -4y^6/x^4


    I got -4x^-4 y^-6

    I know I have to flip it

    So y can't I get
    y^6 / 4x^4
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  4. #4
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    Re: positive exponents

    Quote Originally Posted by Candy101 View Post
    Oh I see Wht I did wrong. I forgot about the x^-2 . Which cancels out!


    Thanks


    (2x^-2 y)^3 / -2x^-2 y^-3

    For this one I can't understand why he got -4y^6/x^4


    I got -4x^-4 y^-6

    I know I have to flip it

    So can't I got
    y^6 / 4x^4
    Why not learn latex, so that we can easily comprehend what you're trying to say? Is this the initial expression:

    \frac{(2x^{-2}y)^3}{-2x^{-2}y^{-3}}
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  5. #5
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    Re: positive exponents

    Quote Originally Posted by Candy101 View Post
    (2x^-2 y)^3 / -2x^-2 y^-3
    For this one I can't understand why he got -4y^6/x^4
    Why not learn to use some basic LaTeX code.
    [TEX]\frac{(x^{-2}y)^3}{(-2x^{-2}y^{-3})}[/TEX] gives \frac{(x^{-2}y)^3}{(-2x^{-2}y^{-3})}

    \frac{(x^{-2}y)^3}{(-2x^{-2}y^{-3})}=-\frac{y^6}{2x^4}
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  6. #6
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    Re: positive exponents

    Yeah
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  7. #7
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    Re: positive exponents

    Quote Originally Posted by Candy101 View Post
    Oh I see Wht I did wrong. I forgot about the x^-2 . Which cancels out!


    Thanks


    (2x^-2 y)^3 / -2x^-2 y^-3

    For this one I can't understand why he got -4y^6/x^4


    I got -4x^-4 y^-6

    I know I have to flip it

    So y can't I get
    y^6 / 4x^4
    (2x^-2 y)^3= 8x^-6y^3. The denominator, 1/(-2x^-2y^-3), becomes (-1/2)x^2y^3

    8(-1/2)= -4. x^-6(x^2)= x^{-4}. y^3(y^3)= y^6

    So that is -4x^{-4}y^6 which, using only positive exponents, is -4y^6/x^4. Again, 8/-2 is -4, not -1/4.
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