7.Binomial Theorem
normal

If ${}^{21}{C_1} + 3.{}^{21}{C_3} + 5.{}^{21}{C_5} + ......19{}^{21}{C_{19}} + 21.{}^{21}{C_{21}} = k$ Then number of prime factors of $k$ is

A

$1$

B

$2$

C

$3$

D

$4$

Solution

$\mathrm{k}=\frac{21\left((1+1)^{20}+(1-1)^{20}\right)}{2}=21 \times 2^{19}=3 \times 7 \times 2^{19}$

Standard 11
Mathematics

Similar Questions

Start a Free Trial Now

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