I have this problem with equation h=15+20t-2t^2 object throwen from tower

I must making graph to show time of flight

Then show greatest height reached.

How high is building

And how long did it take for object to hit.

1 I thinking for graph formula must be xv=-b/2a

which is -20/-2x2=-20/-4=5 this is for my x.

can you please showing me how for getting my y .

when i am knowing this i think i can do rest of problems,

Thanksing you