Problem a
Find out the first difference and second difference
x=6 y=7
x=7 y=4 4-7=-3
x=8 y=3 3-4=-1 -1-(-3)=2
x=9 y=4 4-3=1 1-(-1)=2
x=10 y=7 7-4=3 3-1=2
x=11 y=12 12-7=5 5-3=2
Remember that
If the second difference is the same value, the model will be quadratic
In this problem, the second difference is the same value
therefore
The function is a quadratic function