The coefficient of x4in the expansion of (1+x+x2)10 is__________
General term =10!α!β!γ!×xβ+2γ, where α+β+γ=10
For coefficient of x4,β+2γ=4
So, the possible sets will be
γ=0,β=4,α=6 ⇒ 10!6!4!0!=210γ=1,β=2,α=7⇒10!7!2!1!=360 γ=2,β=0,α=8⇒10!8!0!2!=45
Total = 615