$c)(2x+y^2)^3$
$=(2x)^3+3×(2x)^2×y^2+3×2x×(y^2)^2+(y^2)^3$
$=8x^3+3×2x^2y^2+3×2xy^4+y^6$
$=8y^3+6x^2y^2+6xy^4+y^6$
`f)(2/3x^2-1/2)^3`
`=(2/3x^2)^3-3×(2/3x^2)^2×1/2+3×2/3x^2×(1/2)^2+(1/2)^3`
`=8/27x^6-3×4/9x^4×1/2+3×2/3x^2×1/4+1/8`
`=8/27x^6-2/3x^4+1/2x^2+1/8`
$h)(x-3y)(x^2-3xy+9y^2)$
$=(x-3y)[x^2-3xy+(3y)^2]$
$=x^3+(3y)^3$
$=x^3+27x^3$
$@ThanhTruc2008$