InterviewSolution
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InterviewSolution
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The first , second and the last terms of an A.P. are `a ,b , c`respectively. Prove that the sum is `((a+c)(b+c-2a))/(2(b-a))`. |
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Answer» `1^(st)` term=a `2^(nd)`term=b `3^(rd)`term=c Common diff,d=(b-a) c=a+(n-1)(b-a) c-a=(n-1)(b-a) `n-1=(c-a)/(b-a)` `n=(c-a)/(b-a)+1` `n=(c-a+b-a)/(b-a)=(b+c-2a)/(b-a)` `S=n/2(a+l)` `S=(b+c-2a)/(2(b-a))*(a+c)` `S=((a+c)(b+c-2a))/(2(b-a))`. |
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