@Markiyan Hirnyk 

If I want to describe the region between two funtions, say, c+3<0 and c+5>0, what kind of workaround can I use?

Thank you.

@Markiyan Hirnyk 

Actually the situation is that 

with(plots):

inequal((2*c-1)/(3*c-1),c=0..1,Alpha=0..1)

produces an empty plot, while

with(plots):

inequal((2*c-1)/(3*c-1),c=0..1.5,Alpha=0..1)

produces the right answer. 

the only difference between the two orders is the range of variable 'c'. 

I wonder why.

Thx a lot.

P.S. Do you know where to find the patch to fix the bug you mentioned?