`#tnvt`
`a)(2x^2+1/3)^3`
`=(2x^2)^3+3.(2x)^2 .1/3+3.2x.(1/3)^2+(1/3)^3`
`=8x^6+4x^2+2/3x+1/27`
`b)(2x^2y-3xy)^3`
`=(2x^2y)^3-3.(2x^2y)^2 .3xy+3.2x^2y .(3xy)^2-(3xy)^3`
`=8x^6y^3-36x^5y^3+54x^4y^3-27x^3y^3`
`c)(-3xy^4+1/2x^2y^2)^3`
`=(-3xy^4)^3+3.(-3xy^4)^2 .(1/2x^2y^2)+3.(-3xy^4).(1/2x^2y^2)^2+(1/2x^2y^2)^3`
`=-27x^3y^12+27/2x^4y^10-9/4x^5y^8+1/8x^6y^6`
`d)(-1/3ab^2-2a^3b)^3`
`=(-1/3ab^2)^3-3.(-1/3ab^2)^2 .2a^3b+3.(-1/3ab^2).(2a^3b)^2-(2a^3b)^3`
`=-1/27a^3b^6-2/3a^5b^5-4a^7b^4-8a^9b^3`
