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Question

Question: If the number of terms in \(\left( x + 1 + \frac{1}{x} \right)^{n}\) (n Î I<sup>+</sup>) is 401 then...

If the number of terms in (x+1+1x)n\left( x + 1 + \frac{1}{x} \right)^{n} (n Î I+) is 401 then n is greater than-

A

201

B

200

C

199

D

202

Answer

199

Explanation

Solution

(x+1+1x)n\left( x + 1 + \frac{1}{x} \right)^{n}= (1+x+x2)nxn\frac{(1 + x + x^{2})^{n}}{x^{n}}

(1 + x + x2)n is the form a0 + a1x + a2x2 +.....+ a2nx2n

which contains 2n + 1 terms

2n + 1 = 401 ̃ n = 200