(2x+3y)³=
(2x+3y)(2x)²+2•2x•3y+(3y)²)=
(2x+3y)(2²x²+2•2x•3y+(3y)²)=
(2x+3y)(4x²+2•2x•3y+3²y²)=
(2x+3y)(4x²+2•2x•3y+9y²)=
(2x+3y)(4x²+12xy+9y²)=
2x(4x²+12xy+9y²)+3y(4x²+12xy+9y²)=
8x³+24x²y+18xy²+3y(4x²+12xy+9y²)=
8x³+24x²y+18xy²+12yx²+36y²x+27y³=
8x³+(24x²y+12x²y)+(18xy²+36xy²)+27y³=
8x³+36x²y+54xy²+27y³
