# Not sure if I got this problem right, can someone verify?

• Sep 14th 2010, 07:51 PM
gustahfan
Not sure if I got this problem right, can someone verify?
(3xy^-2)^2(-2x^-4y)^3 / (x^-3y^2)^-3

I tried to check problem and of course it says my answer is wrong, but I can't figure out why!

I got:

-72y^5/x^19
• Sep 14th 2010, 08:05 PM
undefined
Quote:

Originally Posted by gustahfan
(3xy^-2)^2(-2x^-4y)^3/(x^-3y^2)^-3

I tried to check problem and of course it says my answer is wrong, but I can't figure out why!

I got:

-72y^5/x^19

Hmm I get what you get.

$\dfrac{(3xy^{-2})^2(-2x^{-4}y)^3}{(x^{-3}y^2)^{-3}} =(3xy^{-2})^2(-2x^{-4}y)^3(x^{-3}y^2)^3$

$=(9x^2y^{-4})(-8x^{-12}y^3)(x^{-9}y^{6})=(9)(-8)x^{2-12-9}y^{-4+3+6}=\dfrac{-72y^5}{x^{19}}$

What does your book say? (Or is it that your solution is getting rejected by an automatic checker? I have not worked with those, but perhaps it has to do with typesetting or putting the answer in a form the computer will recognize.)
• Sep 14th 2010, 08:08 PM
Educated
$\dfrac{(3xy^{-2})^2 \times (-2yx^{-4})^3}{(x^{-3} \times y^2)^-3}$

Is this your equation? If it is, then $\frac{-72y^5}{x^{19}}$ is correct.

I don't know if you meant -2x^(-4y) or -2x^-4 * y.
• Sep 14th 2010, 08:24 PM
gustahfan
Thank you Undefined and Educated. Yes the way that undefined wrote it out was correct. I tried the [tex] formatting but it came out funky. I was checking it on mathway.com. And it came out with something like:

$9y^2/{x^19}$.

Again thanks for the replies, I knew I was right!
• Sep 14th 2010, 08:28 PM
undefined
Quote:

Originally Posted by gustahfan
Thank you Undefined and Educated. Yes the way that undefined wrote it out was correct. I tried the [tex] formatting but it came out funky. I was checking it on mathway.com. And it came out with something like:

$\frac 9y^2/{x^19}$.

Again thanks for the replies, I knew I was right!

Glad your problem is solved. Regarding LaTeX, you can double click on the LaTeX above to see how it was done. Some useful commands are \frac and \dfrac, also important are braces {}.
• Sep 14th 2010, 09:00 PM
Educated
Best way to learn LaTeX is to read the tutorial.
LaTeX Tutorial

I find that Wolfram|Alpha is a good maths computational website. Just remember to use brackets.
• Sep 15th 2010, 11:05 PM
RHandford
Hi All

This is also a helpful graphical interface to LaTeX, the script output can be copied and posted to site.
It can be found here