`(x-2)(x^{2}-5x+1)-x(x^{2}+11)`
`=x^{3}-5x^{2}+x-2x^{2}+10x-2-x^{3}-11x`
`=-7x^{2}-2`
`[(x^{2}-2xy+2y^{2})(x+2y)-(x^{2}+4y^{2})(x-y)]2xy`
`=(x^{3}+2x^{2}y-2x^{2}y-4xy^{2}+2xy^{2}+4y^{3}-x^{3}+x^{2}y-4xy^{2}+4y^{3})2xy`
`=(-6xy^{2}+x^{2}y+8y^{3})2xy`
`=-12x^{2}y^{3}+2x^{3}y^{2}+16xy^{4}`