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  • If coefficient of second, third and fourth terms of <img alt="\left ( 1+x \right )^{2n}" src="http://entrancecorner.oncodecogs.com/gif.latex?%5Cleft%20%28%201&plus;x%20%5Cright%20%29%5E%7B

If coefficient of second, third and fourth terms of \left ( 1+x \right )^{2n} are in AP then which relation is true?

Option: 1

x^2-9x+7=0


Option: 2

2x^2-9x+7=0


Option: 3

2x^2-3x+7=0


Option: 4

x^2-3x+7=0


Answers (1)

best_answer

Given \binom{2n}{1},\binom{2n}{2},\binom{2n}{3} are in AP

Thus

2*\binom{2n}{2}=\binom{2n}{1}+\binom{2n}{3}

\left ( 2n-1 \right )=1+\frac{\left ( 2n-1 \right )\left ( n-1 \right )}{3}

\Rightarrow 2n^2-9n+7=0

Posted by

vishal kumar

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