You can
put this solution on YOUR website!
and
are you sure this is what you need

or you need
I guess that cubic function is what you need:

and

to see what changes we get if we chaging
here is the graph of

:
now, watch the graph if
a.
we can take

and see what is different if we compare it to previous
now, watch the graph if
b. –1 < a < 0......let

, do you see any difference?
now, watch the graph if
c.

<

<

......let

, do you see any difference?
now, watch the graph if
d.

<

.......let
If a getting smaller and smaller then

, graph is getting closer and closer to from

to

and lies in II and IV quadrant.
Let see the graph for

which is very close to

…….it is almost straight line which tend to lie on

but still goes through II and IV quadrant.
Let see the graph for

which is very distant from

…….it is almost straight line which tend to lie on y-axis
If a getting greater and greater then

, graph is getting closer and closer to from

to

and lies in II and IV quadrant.
Let see the graph for

which is very close to

…….it is almost straight line which tend to lie on

but still goes through I and III quadrant.
Let see the graph for

which is very distant from

…….it is almost straight line which tend to lie on

but still goes through I and III quadrant.