几道初一数学题，我急~~~~~~~~~~~~~

1.如果xz/y<0,yz>0,那么x_<__0(填<,>,=.)

2.若a/|a|+|b|/b=-2,则|ab|/ab=__1___

3.如果对于任意非零有理数a,b定义运算x如下:axb=a-b/ab,求5x(4x3)
x是一种符号.
4x3=(4-3)/(4×3)=1/12
5x(4x3)=5x(1/12)=(5-1/12)/(5×1/12)=(59/12)/(5/12)=59/5

4.若ab不等于0,则a/|a|+|b|/b的取值不可能是( B )
A.0 B.1 C.2 D.-2

1.x<0

2.|ab|/ab=1

3.
5x(4x3)
=5x[(4-3)/4*3]
=5x(1/12)
=[5-(1/12)]/5*(1/12)
=59/5

4.选B
若a>0,b>0,a/|a|+|b|/b=2
若a<0,b<0,a/|a|+|b|/b=-2
若a<0,b>0,或a>0,b<0,a/|a|+|b|/b=0

1.x<0
2. -1
3. 59/5 =5x{(4-3)/(4*3)}=5x{1/12}
=(5-1/12)/(5*1/12)=59/5
4.B