Answer: 10
Plug in the given x values and see which result is the largest
Plug in x = 0 ---> x^2+1 = 0^2 + 1 = 1
Plug in x = 1 ----> x^2 + 1 = 1^2 + 1 = 2
Plug in x = 2 ----> x^2 + 1 = 2^2 + 1 = 5
Plug in x = 3 ---> x^2 + 1 = 3^2 + 1 = 10
The range is therefore {1, 2, 5, 10} which is just the set of possible outputs.
We see that y = f(x) = 10 is the largest output of the range if the domain is restricted to the set {0, 1, 2, 3}