y+3/4x+y+3/4x,x平方/x-2-4/x-2,x+4y/x+y+2x-y/x+y 上面是分式的加法与减法

y+3/4x+y+3/4x,
=2y+6/4x
=2y+3/2x

x平方/x-2-4/x-2,
=(x²-4)/(x-2)
=(x-2)(x+2)/(x-2)
=x+2

x+4y/x+y+2x-y/x+y
=(x+4y+2x-y)/(x+y)
=(3x+3y)/(x+y)
=3(x+y)/(x+y)
=3

3-x/2-x-x平方/2-x-x+1/x-2
=(x-3)/(x-2)+x²/(x-2)-(x+1)/(x-2)
=(x-3+x²-x-1)/(x-2)
=(x²-4)/(x-2)
=(x-2)(x+2)/(x-2)
=x+2

3ab平方+1/（a-b)平方-1+3a平方b/(b-a)平方
=(3ab²+1-1-3a²b)/(a-b)²
=3ab(b-a)/(b-a)²
=3ab/(b-a)