题目先化简,再求值:3(2x2y−3xy)−(xy+6x2y)3(2x^{2}y-3xy)-(xy+6x^{2}y)3(2x2y−3xy)−(xy+6x2y),其中x=2x=2x=2,y=−1y=-1y=−1.知识点：整式化简求值章节：数与式 / 整式
