Sketch the graphs the following function:

f(x) = 10 + 3x -x^2

I know how you would go about sketching this. You would first have to find the x and y-intercepts however, I am having trouble finding the x-intercepts.

The thing is I've never factorised a quadratic where the leading, ax^2 is negative. Note: It's just the '-' in the x^2 that's confusing me. I've tried a few times with failure:

-x^2 + 3x + 10 = 0

-(x + 5)(x - 2) = 0

however, I think it's supposed to be factorised to (5 -x)(2 + x)

anyway, how would I go about contiuning to solve for the values of x for which the y values would equal 0? please outline each step slowly for me so I'll understand.

Thank you.