Question

2nCr=
what and why plzz tell
a]2nCn-r.
b]2nC2n-r​

Answer 1

The answer is b] 2nC2n-r

Let's take two no.s: 10 and 3

Now, let 2n = 10 and r = 3

=10C3

but 10C3 is also equal to 10C7

∵ We got 7 by 10(2n)-3(r)

⇒2nCr = 2nC2n-r