Question

Find the coefficient of x^5 in expansion of (1+x)^22 +_ _ _ _ (1+x)^30

Answer 1

Hey,

(1+x)21+(1+x)22+.........(1+x)30

=(1+x)21.(1+(1+x)+(1+x)2+........((1+x)9)

=(1+x)21{(1+x)10−1(1+x)−1}

=1x[(1+x)31−(1+x)21]

∴ Coeff. of x5 in this expansion=

Coeff. of x6 in the expansion [(1+x)31−(1+x)21]

=31C6−21C6.

HOPE IT HELPS YOU:-))

Answer 2

HOPE IT HELPS ✌

student-name Kamal answered this
coefficient of x^6 is (1-x)^31-(1-x)^10
31c6 - 10 c 6..