题目先化简再求值:5x2−[2xy−3(13xy−5)+6x2]5x^{2}-[2xy-3(\frac{1}{3}xy-5)+6x^{2}]5x2−[2xy−3(31xy−5)+6x2].其中x=−2x=-2x=−2,y=12y=\frac{1}{2}y=21.知识点：整式化简求值章节：数与式 / 整式
