Answer:
x^2 +4
Explanation:
It is perhaps easiest to simply try the answers to see what works. x=1 corresponds to the first term, so the different answer choices will give that value as ...
3x² +4 = 3 +4 = 7
x² +4x = 1 + 4 = 5 . . . . possible solution
x² +4 = 1 +4 = 5 . . . . possible solution
x² +5 = 1 +5 = 6
Then for x=2, we want the result to be 8. The two choices we've identified so far give ...
x² +4x = 2² +4·2 = 12
x² +4 = 2² +4 = 8 . . . . . this is the solution