How to do the vertex is using the formula -b/2a
your a=-9 and b is -18 but it going to become +18 because you are multiplying the -(-18) which there a 1 in front the neg. you going to multiply the -9 by 2 and do 18/18 so your x= -1. You got your x, you going to put in the equation as y=-9(-1)^2-18(-1)-1 then you got your y... hope this is helpful :)
