# Math Help - Hah, okay. I've got one hour to turn this in...

1. ## Hah, okay. I've got one hour to turn this in...

And I'm terrible at this stuff..If someone wouldn't mind walking me through these, I'd be super grateful.

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With this one, I know i need to add up the nominator and denominator by finding a common denominator for each..then to take:

[(t^2-s^2)/(s^(2)t^(2))]/[(t+s)/(st)]

But then I'm stuck.

2. #1)What are you supposed to do here?

#2) Factor $s^2-9$. You should get $(s+3)(s-3)$ and you get some nice cancellation.

#3)Multiply the whole thing by (st)/(st)

3. Or notice you can apply the difference of squares formula to the numerator and notice that something cancels :
$\frac{\displaystyle \frac{1}{s^2} - \frac{1}{t^2}}{\displaystyle\frac{1}{s} + \frac{1}{t}} = \frac{\displaystyle\left(\frac{1}{s} - \frac{1}{t}\right)\left(\frac{1}{s} + \frac{1}{t}\right)}{\displaystyle\frac{1}{s} + \frac{1}{t}}$

4. Originally Posted by o_O
Or notice you can apply the difference of squares formula to the numerator and notice that something cancels :
$\frac{\displaystyle \frac{1}{s^2} - \frac{1}{t^2}}{\displaystyle\frac{1}{s} + \frac{1}{t}} = \frac{\displaystyle\left(\frac{1}{s} - \frac{1}{t}\right)\left(\frac{1}{s} + \frac{1}{t}\right)}{\displaystyle\frac{1}{s} + \frac{1}{t}}$
Much more elegant.

5. Hello,
$\frac{6ab-8b^2}{15a^2-20ab}=\frac{2b(3a-4b)}{5a(3a-4b)}$
$=\frac{2b}{5a}$