计算:(-1-2a)(2a-1)=______.
(-1-2a)(2a-1),
=(-1)2-(2a)2,
=1-4a2.
What would you do _ your father wouldn't help you? [ ]
A. why
B. because
C. if
双效吸收式冷水机组的溶液循环流程有串联流程、并联流程和串并联流程三种。