Answer:
(1;-4).
Step-by-step explanation:
1. zeros of the given function are: -1 and 3, then
2. the x-coordinate of the vertex is 0.5*(3-1)=1.
3. the y-coordinate of the vertex can be calculated if to substitute x=1 into the given equation:
y=(1+1)(1-3)=-4.
PS. this way is not the only one.
