Question

How do I get the plot coordinates from f(x)=-5x^2+6x+9 if x is 0?

Answer 1

it will be just the y-intercept if x=0 .

Answer 2

In other words: "How do I find y if x=0, and how do I use these two numbers to write the coordiates of the specified point on the graph?

Your function is f(x)=-5x^2+6x+9. You are asked to let x=0 and find the corresponding y. Please do that now. In every instance where you see x, replace that with (0). What does this give you for y?