1.已知|a|=5,|b|=3,且|a+b|=a+b,求a-b的值2.若|x+1/2|+|y-1/3|+|z+1|=0,试求x+y-Z3.计算：|-3/7|-[-(-1\4)]+(-2/3)+[-(-1/4)]-0.254.当x=-1/3,y=3/4,z=-1/2,w=5/12时,求x-y-z+w的值

Question

1.已知|a|=5,|b|=3,且|a+b|=a+b,求a-b的值
2.若|x+1/2|+|y-1/3|+|z+1|=0,试求x+y-Z
3.计算：|-3/7|-[-(-1\4)]+(-2/3)+[-(-1/4)]-0.25
4.当x=-1/3,y=3/4,z=-1/2,w=5/12时,求x-y-z+w的值

Answer 1

1.2或8
a=5 b=3或a=5 b=-3
2.x=-1/2 y=1/3 z=-1
所以x+y-Z=5/6
3.-1/84
4.-1/6