49x^4+4y^4/7x^3y+2xy^3,其中7x=2y

问题描述:

49x^4+4y^4/7x^3y+2xy^3,其中7x=2y

∵y=7x/2
∴ 49x^4+4y^4/7x^3y+2xy^3
=﹙49x^4+4y^4﹚/﹙7x^3y+2xy^3﹚
=﹙49+49²/4﹚/﹙49/2+7³/4﹚
=53/9