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Quick bit of rearrangment... think I'm losing the plot, can someone help?!

All in the title... it's just a really simply bit of rearrangement, but I don't understand how the result that is obtained, is obtained. Think I'm going mad after too much revision, I can tell it's easy but I'm not seeing it properly!

All is revealed:



I have obtained q2 = (9 - 9b^2 + 18b)/(4b^2 - 8) instead, and don't quite see how I've gone wrong. When the fraction is on the top of the fraction, is it okay for me to just take that bottom half of the fraction (2b^2 - 4) down to the bottom of the overall fraction?

Any help appreciated. Thanks.
Original post by Jackus
All in the title... it's just a really simply bit of rearrangement, but I don't understand how the result that is obtained, is obtained. Think I'm going mad after too much revision, I can tell it's easy but I'm not seeing it properly!

All is revealed:



I have obtained q2 = (9 - 9b^2 + 18b)/(4b^2 - 8) instead, and don't quite see how I've gone wrong. When the fraction is on the top of the fraction, is it okay for me to just take that bottom half of the fraction (2b^2 - 4) down to the bottom of the overall fraction?

Any help appreciated. Thanks.


Using a different example, you have in effect: a+bcd\dfrac{a+\frac{b}{c}}{d}

You need to put the whole of the numerator (of the overall fraction) over "c" before you can "pull it down".

Thus:

=ac+bcd=\dfrac{\frac{ac+b}{c}}{d}

=ac+bcd=\dfrac{ac+b}{cd}
(edited 12 years ago)
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Jackus
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Original post by ghostwalker
Using a different example, you have in effect: a+bcd\dfrac{a+\frac{b}{c}}{d}

You need to put the whole of the numeator (of the overall fraction) over "c" before you can "pull it down".

Thus:

=ac+bcd=\dfrac{\frac{ac+b}{c}}{d}

=ac+bcd=\dfrac{ac+b}{cd}


Ahhhh, I have always been unsure about that rule, and stumbled through!

Thank you very much!
Original post by Jackus
Ahhhh, I have always been unsure about that rule, and stumbled through!

Thank you very much!


No problem.

What you've done in effect is to multiply the top and bottom of the overall fraction by "c".

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