A:( m1 + m2 ) v0 / ( m1 + m2 + m3 )
B:m2v0 / ( m2 + m3 )
C:m2v0 / ( m1 + m2 + m3 )
D:上述三答案均不对
计算:3m2•(﹣2mn2)2=____
Tom was so careless that he his right arm when he was riding to school
yesterday.