7.Binomial Theorem
medium

${C_1} + 2{C_2} + 3{C_3} + 4{C_4} + .... + n{C_n} = $

A

${2^n}$

B

$n.\,\,{2^n}$

C

$n.\,\,{2^{n - 1}}$

D

$n.\,\,{2^{n + 1}}$

Solution

(c) Trick : Put $n = 1,\,\,2,\,\,3,….$

${S_1} = 1,\,\,{S_2} = 2 + 2 = 4$

Now by alternate $(c)$, put $n = 1,\,\,2$

 ${S_1} = {1.2^0} = 1,{S_2} = {2.2^1} = 4$

Standard 11
Mathematics

Similar Questions

Start a Free Trial Now

Confusing about what to choose? Our team will schedule a demo shortly.