1. Combine like term:
f(x) = 15 + 3x
2. Find x:
a= 0, b= 3x, c= 15
x = -b/2(a)
x= -(3)/2(0)
x= 0
3. Find y (FYI: f(x) is also the same thing as y)
f(x) = 12 + 3x + 3 <- now you know what is x, plug it in !
f(x) = 12 + 3(0) + 3
f(x) = 15 or y = 15
4. Vertex = (x,y)
Vertex = (0, 15) <- that’s ur answer :D