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Mathematics 15 Online
OpenStudy (anonymous):

Is anyone available to help with rewriting negative exponents?

OpenStudy (tkhunny):

Only if you write the problem statement and demonstrate your best work.

OpenStudy (anonymous):

i will :)

OpenStudy (anonymous):

x^-2 - y^-2 \ x^-3 + y^-3

OpenStudy (tkhunny):

Wish I could read that. Should it say \(\dfrac{x^{-2} - y^{-2}}{x^{-3} + y^{-3}}\)? It doesn't say that at all. I'm totally guessing.

OpenStudy (anonymous):

the negative exponents on the bottom should be 3

OpenStudy (tkhunny):

Which they are. If that is what you intended, you should have written this: (x^-2 - y^-2) / (x^-3 + y^-3) What a difference parentheses can make!

OpenStudy (anonymous):

ok thank you :)

OpenStudy (tkhunny):

IF it were me, I would multiply both numerator and denominator by x^3.

OpenStudy (anonymous):

i tried multiplying the numerator and denominator by x^3y^3 and ended up with (xy^3 - x^3y) / (y^3 + x^3) but not sure if this is correct, and then how to simplify

OpenStudy (tkhunny):

Give that another try. You should get: \(\dfrac{x - x^{3}y^{-2}}{1 + x^{3}y^{-3}}\) There should not yet be any positive y exponents.

OpenStudy (anonymous):

the assignment is to rewrite the expression so that there are only positive exponents and then simplify

OpenStudy (tkhunny):

Whoops. I see you jumped ahead of me. So now you have: \(\dfrac{xy^{3} - yx^{3}}{y^{3} + x^{3}}\)

OpenStudy (tkhunny):

Okay, now it's time to see if we can factor anything. The numerator looks easy enough: xy(y^2 - x^2) = xy(x+y)(x-y) Do you see all that?

OpenStudy (anonymous):

thank you, yes i see that

OpenStudy (anonymous):

can the denominator be factored?

OpenStudy (tkhunny):

This is a great secret. Remember that a difference of SQUARES can be factored but a SUM of squares cannot! This is not so for cubes. Both a SUM and a DIFFERENCE can be factored. \(y^{3} + x^{3} = (y+x)(y^{2} - yx + x^{2})\) \(y^{3} - x^{3} = (y+x)(y^{2} + yx + x^{2})\)

OpenStudy (anonymous):

thank you so much:) would you be willing to walk through another problem with me?

OpenStudy (tkhunny):

Post on a separate thread, please. I still have a few minutes.

OpenStudy (anonymous):

k thank you

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