How do I do this? I am not entirely sure

Answer:
[tex]n^2+3\\(n+1)^2[/tex]
Step-by-step explanation:
[tex]n^2+3[/tex]
[tex](1)^2+3=4\\(2)^2+3=7\\(3)^2+3=12\\(4)^2+3=19[/tex]
[tex](n+1)^2[/tex]
[tex]((1)+1)^2=4\\((2)+1)^2=9\\((3)+1)^2=16\\((4)+1)^2=25[/tex]