Question 70015
Set y equal to the function you were given.  This results in the equation:

{{{y=x^2-2x-8}}}

Now think about the general structure of a graph.  If you have a point on the Y-axis,
what is the value of X for that point.  Every point on the Y-axis has a corresponding
X value of zero!!!  Think of +3 on the Y-axis.  This would be the point (0,+3).  Similarly
the point -5 on the Y-axis would be (0, -5) and so on.

So for the above equation we can simply set x equal to zero to find the corresponding
value of y that satisfies the equation.  Start with:

{{{y=x^2-2x-8}}}

Plug in zero for x.  This causes the terms that contain an x to be zero.  What you are
left with is:
{{{y=0 + 0 - 8}}} which simplifies to just {{{y = -8}}}

The Y-intercept occurs at y = -8 or at the point (0,-8).  It's harder to explain than it
is to just set x equal to zero and determine what is left on the right side of the equation.

Hope this helps you understand how to find Y intercepts.