Question

how do I graph the quadratic function in intercept form for y=(x+3)(x-5)

Answer 1

you can see the x-intercepts right off. They are the roots: -3 and 5

As for the y-intercept, that is just -15

For excellent graphing help visit

http://rechneronline.de/function-graphs/

and type in your function, but express all operators explicitly:

(x+3)*(x-5)

To get a better picture, increase the x range to -10 to 10 and the y-range to -20 to 20