甲做180个机器零件与乙做240个机器零件所用的时间相同.已知两人每小时工作140个零件,则甲,乙两人每小时各做多少个机器零件?
假设甲乙每个小时各做x和y个
180/x=240/y
x+y=140
解得:x=60个 y=80个
解方程
（1）7/（x+2)=(1-3x)/(x+2）-2
7/（x+2)=(1-3x)/(x+2）-(2x+4)/(x+2)
7/（x+2)=(-5x-3)/(x+2)
7(x+2)=(-5x-3)*(x+2)
7=-5x-3
x=-2
(2)[(x+2)/(x-1)]-[5/(x的平方-1）]=1
[(x+2)*(x+1)/(x-1)*(x+1)]-[5/(x²-1)=1
(x²+3x+2)-5=x²-1
3x-3=-1
x=2/3
(3)[(x-4)/9x-5)]+[(x-8)/(x-9)]=[(x-7)/(x-8)]+[(x-5)/(x-6)]
过程一定要详细
计算：
(1)(3-m)/(2m-4)÷{m+2-[5/(m-2)]}
m+2-[5/(m-2)]=(m²-4)/(m-2)-5/(m-2)=(m²-9)/(m-2)
(3-m)/(2m-4)÷{m+2-[5/(m-2)]}
=(3-m)/2(m-2)*(m-2)/(m²-9)
=-1/2m-6
=1/(6-2m)
(2)(x-3)/(2x-4)÷{[5/(x-2)]x-2}
{[5/(x-2)]x-2}=(5x/x-2)-(2x-4/x-2)=(3x+4)/(x-2)
(x-3)/(2x-4)÷{[5/(x-2)]x-2}
=(x-3)/(2x-4)÷(3x+4)/(x-2)
==(x-3)/(2x-4)*(x-2)/(3x+4)
=(x-3)/(6x+8)