You can put this solution on YOUR website!
Here is what I have done
x=- b/2a <=== ok
x=- -2/2(1) <=== ok
x=2/2(1) <=== ok
x=2/x <=== should be 2/2
x=1 <=== ok
f(1)=(1)^2-2(1)-8 <=== ok
f(1)=(1)-2(1)-8 <=== ok
f(1)=(1)-2-8 <=== ok
f(1)=-1-9 <=== you probably meant -1 - 8
f(1)=-9 <=== ok
You used a good process. And the point you found (1,-9) is the correct point. But you didn't
mention whether is was a maximum or a minimum point. It is a minimum point and you can tell
that because the x^2 term is preceded by a + sign. If the x^2 term had been -x^2 then the
point you found would have been a maximum point on the curve.
You have the correct idea on how to do the problem.
Another thing you can tell about this graph from the work you have done is that the graph
crosses the x-axis at two points. You can tell this because the minimum point occurs where
y = -9. The graph is a parabola that rises from that point. Therefore, in rising the
parabola must cross the x-axis in two locations ... one to the left of x = +1 and one to
the right of x = +1 on the x-axis. Hope this makes sense. Anyhow, good work!!!