A:3﹣1=﹣3
B:9 =±3
C:(ab2)3=a3b6
D:a6÷a2=a3
Tom didn't go hiking with his classmates ____ his illness.
下列有关生物圈的范围及其定义的叙述中,正确的是( )
甲和乙两人玩“打弹珠”游戏,甲对乙说:“把你珠子的一半给我,我就有10颗珠子”,乙却说:“只要把你的13给我,我就有10颗”,如果设乙的弹珠数为x颗,甲的弹珠数为y颗,则列出方程组正确的是( )