Question 424464
You don't say what you want to do with this quadratic function.
I expect that you are supposed to graph it.
{{{y = -x^2+8x-15}}}
You can generate an input/output table to get a few points which you can then plot on a coordinate graph sheet.
Then, with the careful use of a french curve, you can sketch the resulting parabola.
Here's a start: Substitute a value for x and calculate the corresponding value of y.
Input(x)|||Output(y)
-------------------
****0***|||***-15***
****1***|||****-8***
****3***|||*****0***
****4***|||*****1***
****5***|||*****0***
...and here's what it should look like:
{{{graph(400,400,-5,10,-10,5,-x^2+8x-15)}}}