下列各组单项式中,是同类项的为( )
A:﹣x2y与x2y2
B:x2y2与2xy
C:﹣x2y与3x2y
D:xy2与x2y
已知常数a、b、c都是实数,f(x)=ax3+bx2+cx-34的导函数为f'(x),f'(x)≤0的解集为{x|-2≤x≤3},若f(x)的极小值等于-115,则a的值是( )
____ (lucky), his second mother was very kind to him.
What about ____ (go) to the Great Wall for our summer holiday?
买5元1千克的茶叶和8元1千克的茶叶共10千克,用去71元。这两种茶叶各买了多少千克?