题目先化简,再求值:3(x2−2xy)−(2x2+4xy)+2x23(x^{2}-2xy)-(2x^{2}+4xy)+2x^{2}3(x2−2xy)−(2x2+4xy)+2x2,其中x=−1x=-1x=−1,y=15y=\frac{1}{5}y=51.知识点：整式加减运算法则章节：未标注
