I'm literally doing this right now for homework. Use the equations y= ax^2+bx+c and -b/2a
Now plug in -13/2(-1)= -13/-2= 6.5 is the x coordinate
Plug in 6.5 for x into y= -1x^2+13x
-1(6.5)+13(6.5)= 78
Now I don't know if (6.5,78) is correct for the vertex but I tried. I'm sorry if I'm wrong
