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Can anybody explain the basics of componendo and dividendo?

The basic rules to be learnt.

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Vipul Bawa
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Basic rule is that:$eq=if\;\frac{a}{b}\ = \frac{c}{d}$
$eq=then \; \frac{a+b}{a-b} = \frac{c+d}{c-d}$

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Vipul Bawa
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Derivation:
$eq=\frac{a}{b}=\frac{c}{d}\\ add 1\\\Rightarrow\frac{a+b}{b}=\frac{c+d}{d}............(1)\\ subtract 1\\ \Rightarrow\frac{a-b}{b}=\frac{c-d}{d}..........(2)\\ divide (1) by (2)\\ \Rightarrow\frac{a+b}{a-b}=\frac{c+d}{c-d}$

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Yogesh Garg
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another thing you shud keep in mind is :

$eq=\frac{{N}_{1}}{{D}_{1}}=\frac{{N}_{2}}{{D}_{2}}\\ then\;apply\;operation\; \frac{N-D}{N+D}\; on\;both\;sides$

why : it helps us in complex and we are saved from doing errors in the qs where we tend to get confused. of course if you are a pro then this answer is not for you.

This message was edited 1 time. Last update was at 15/06/2008 06:58:03

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APEKSHA SINGHAL
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IF

$eq=\frac{a}{b}=\frac{c}{d}$

THEN
$eq=\frac{a+b}{a-b}=\frac{c+d}{c-d}$

this is the law called componendo and divinendo ie.. adding and subtracting

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