a, `(3a+2)^3=(3a)^3+3.(3a)^2 .2+3.3a.2^2+2^3`
`=27a^3+54a^2+36a+8`
b, `(m^2-1/2 n)^3=(m^2)^3-3.(m^2)^2 .1/2n + 3.m^2 .(1/2 n)^2 - (1/2 n)^3`
`=m^6- 3/2 m^4 n+ 3/4 m^2n^2 - 1/8 n^3`
c, `(x+1)^3-x(x-2)^2-1`
`=(x^3+3x^2+3x+1)-x(x^2-4x+4)-1`
`=x^3+3x^2+3x+1-x^3+4x^2-4x-1`
`=7x^2-x`
d) `(x+1)^3-(x-1)^2-3(x+1)(x-1)`
`=(x^3+3x^2+3x+1)-(x^2-2x+1)-3(x^2-1)`
`=x^3+3x^2+3x+1-x^2+2x-1-3x^2+3`
`=x^3-x^2+5x`