—The coat __________be Mary's. It's for men.
A:Who; must
B:Who; can't
C:Whose;can't
D:Whose; must
已知函数y=xlnx
(1)求这个函数的导数;
(2)求这个函数的图象在点x=1处的切线方程.
牵引索与蒸汽活塞连接的两个滑轮为____ (选填“定滑轮”或“动滑轮”)。
(x﹣1)(x+1)=x2﹣1
(x﹣1)(x2+x+1)=x3﹣1
(x﹣1)(x3+x2+x+1)=x4﹣1
(x﹣1)(x4+x3+x2+x+1)=x5﹣1…
运用上述规律,试求26+25+24+23+22+2+1的值.