6、y=(x-1)/(2-3x)
(1) x∈R且 x≠2/3
2-3x≠0
x≠2/3
(2) x=1
y=0
(x-1)/(2-3x)=0
x=1
(3) y=-2/7
x=3
y=(3-1)/(2-3×3)=-2/7
13、(1) 2/x
x≠0
(2) (2x+1)/(3x+2)
3x+2≠0
x≠-2/3
(3) (3+x^2)/(2x-3)
2x-3≠0
x≠3/2
(4) 2/(x-y)
x-y≠0
x≠y
(5) (a+b)/(a-2b)
a-2b≠0
a≠2b
(6) 2/(x^2-1)
x^2-1≠0
x≠±1