求作:圆O,使它切MN于点A,且半径等于a.
400÷20=____
390+56=____
45×30=____
150×6=____
20+80×4=____
540-190=____
24×50=____
201×4=____
6000÷30=____
9+9×10=____
欲将含有盐酸的氯化钙溶液中和至中性,在不用指示剂的条件下,应加入的试剂是( )
影响冰岛火山活动的板块是()
“Are you really an artist?” Felix asked ____ (curious).