Question

if A and B are coefficients of xᴺ in the expansion of (1+x)²ᴺ and (1+x)²ᴺ⁻¹ then,

A). A=2B
B). A=B
C). 2A=B
D). A/B=(2n)!​

Answer 1

Answer:

Correct option is

B

2

We know that coefficient of x

r

in the expansion of (1+x)

m

is

m

C

r

Thus A=

2n

C

n

;B=

2n−1

C

n

We have

B

A

=

2n−1

C

n

2n

C

n

=

n!n!

(2n)!

(2n−1)!

(n!)(n−1)!

=

n

2n

=2