山地和丘陵的共同点有下列中的
仿照例子写句子。
例子:I watched TV last night. And you?
Did you watch TV last night?
化简求值:3xy2﹣xy﹣2(xy﹣ 32 x2y)+3 xy2+3x2y,其中x=3,y=﹣ 13 .