〔5xy^2(x^2-3xy)-(-3x^2y^3)〕/2x^2y^2=(5x³y² - 15x²y³+3x²y³)/(2x^2y^2)=(5x³y² - 12x²y³)/(2x^2y^2)=(5xy-12y)/2=(5xy/2) - 6y