In the binomial expasion of (a − b)^5 , the sum of 2^(nd) and 3^(rd) term is zero, then (a/b) is


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Question Number 22612 by Tinkutara last updated on 21/Oct/17

$I n t h e b i n o m i a l e x p a s i o n o f {(a - b)}^{5},$ $t h e s u m o f 2^{n d} a n d 3^{r d} t e r m i s z e r o,$ $t h e n \frac{a}{b} i s$
	Answered by ajfour last updated on 21/Oct/17

	$\Rightarrow - 5 a^{4} b + 10 a^{3} b^{2} = 0$ $\Rightarrow \frac{a}{b} = 2 .$
	Commented by Tinkutara last updated on 21/Oct/17

	$B u t i n b o o k a n s w e r g i v e n i s \frac{1}{2} . I s t h i s$ $w r o n g ?$
	Answered by ajfour last updated on 21/Oct/17

	${(a - b)}^{5} = - {(b - a)}^{5}$ $s u m o f 2^{n d} a n d 3^{r d} t e r m$ $= 5 b^{4} a - 10 b^{3} a^{2} = 0$ $\Rightarrow \frac{a}{b} = \frac{1}{2} .$
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