观察下列一串单项式的特点:xy,﹣2x2y,4x3y,﹣8x4y,16x5y,…
(1)按此规律写出第9个单项式;
(2)试猜想第N个单项式为多少?它的系数和次数分别是多少?
They solved the problem in the end. Yet I really don't know .