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October 1st, 2011, 02:10 PM   #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


Thanks.
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October 1st, 2011, 02:33 PM   #2
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Re: Positive Exponents

We are given:



to write using only positive exponents. Multiplying coefficients and like bases, there results:



You incorrectly added exponents on the x terms and got 2 instead of 2 - 2 = 0. This term then becomes 1 and need not be written via the multiplicative identity property, i.e.:



edit: You also have rewritten the original expression as:



The factor in both numerator and denominator divide out, leaving:

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