先化简,再求值: xx2-1÷(x+22x-2-1x-1) ,其中 x=2-1 .
一些历史名词往往被打上时代的烙印。“大串联”、“红卫兵”、“停课闹革命”发生在( )
—I can't agree more. Because we often have more than one choice.
小王的手指不慎划破出血,血液中与伤口止血和避免发炎有关的成分分别是( )