[5xy²（x²-3xy）+（3x²y²）³]÷（5xy）²
=(5x³y²-15x²y³+27x^6y^6)÷(25x²y²)
=[(x²y²)(5x-15y+27x^4y^4)]÷(25x²y²)
=(5x-15y+27x^4y^4)÷25
=5分之1x-5分之3y+25分之27x^4y^4
x^4y^4表示x的4次方y的4次方