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Find the coffiecient of `x^2 y^3 z^4 ` w in the expansion of `(x-y-z+w)^(10)`

Answer» `(X-Y-Z +W)^(10)= underset(P+q+r+s=10) Sigma (n!)/(p ! Q! R ! S! )(x)^p(-y)^q(-z)^r (W)^s`
we want to get `x^2 y^3 z^4` w this implies that p=2,q = 3 ,r = 4 ,s=1
`therefore "Cofficient of " x^2 y^3 z^4 W is (10!)/(2! 3 ! 4 ! 1 !) (-1 )^3(-1)^4= -12600`


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