The coefficient of x 4 in the expansion of 1 + x + x 2 10 is ________

Question

Aicharya · Accepted Answer

General term 10 ! α ! β ! γ ! x β + 2 γ For coefficient of x 4 ⇒ β + 2 γ = 4 γ = 0 , β = 4 , α = 6 ⇒ 10 ! 6 ! 4 ! 0 ! = 210 γ = 1 , β = 2 , α = 7 ⇒ 10 ! 7 ! 2 ! 1 ! = 360 γ = 2 , β = 0 , α = 8 ⇒ 10 ! 8 ! 0 ! 2 ! = 45 Total = 615

The coefficient of x 4 in the expansion of 1 + x + x 2 10 is ________

Solution