A:a3·(-a2)= a5
B:(-ax 2)3=-a x6
C:3x3-x(3x2-x+1)=x2-x
D:(x+1)(x-3)=x2+x-3
最先证实地球是球体的事件是( )
- I really want to join the square dance. Can I learn the dance well?
- Yes, Mom! Nothing is impossible ______ you put your heart into it!