binomial theorem1

Write down the coefficients of the required terms or the constant terms in the expansions of the following.
(2x + y)^10, term in (x^3)(y^7)
It is C(10,3)*(2x)^3*y^7 = 120*8x^3*y^3 = 960x^3y^7
[4(x^2) - (1/2x)]^9, constant term
Constant term is C(9,r)*(4x^2)^r*(-1/x)^(9-r)
so 2r - 9 + r = 0 => r = 3
Constant term C(9,3)*(4x^2)^3*(-1/x)^6 = 84 * 64x^6 * (1/x^6) = 5376