# Reducing question

• Jun 11th 2008, 01:35 AM
onetreehill56
Reducing question
The problem was 4ab^3 / a^3 divided by -12a^4b / ab^2

I know you have to flip the second fraction, then multiply, but I don't understand how you get from that answer to the real answer, -b^4 / 3a^4 well, at least the answer key we were given said that. Any help would be much appreciated
• Jun 11th 2008, 03:58 AM
topsquark
Quote:

Originally Posted by onetreehill56
The problem was 4ab^3 / a^3 divided by -12a^4b / ab^2

I know you have to flip the second fraction, then multiply, but I don't understand how you get from that answer to the real answer, -b^4 / 3a^4 well, at least the answer key we were given said that. Any help would be much appreciated

$\displaystyle \frac{ \frac{4ab^3}{a^3} }{ -\frac{12a^4b}{ab^2} } = \frac{4ab^3}{a^3} \cdot -\frac{ab^2}{12a^4b}$

$\displaystyle = -\frac{4ab^3 \cdot ab^2}{a^3 \cdot 12a^4b}$

$\displaystyle = -\frac{4a^2b^5}{12a^7b}$

$\displaystyle = -\frac{b^4 \cdot 4a^2b}{3a^5 \cdot 4a^2b}$

$\displaystyle = -\frac{b^4}{3a^5}$
so your given answer was off by a factor of a.

-Dan