Q.
If f(x)=(1+x)n, then the value of f(0)+f′(0)+2!f′′(0)+.....+n!f(n)(0) is equal to
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J & K CETJ & K CET 2012Continuity and Differentiability
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Solution:
Given, f(x)=(1+x)n
On differentiating w. r. t. x, we get f′(x)=n(1+x)n−1
Again, differentiating, we get f′′(x)=n(n−1)(1+x)n−2 ∴fn(x)=n(n−1).....3.2.1=n! ∴f(0)+f′(0)+2!f′′(0)+....n!fn(0) =1+n+2!n(n−1)+....+n!n! =nC0+nC1+nC2+...+nCn =2n