Find the nth term Decide whether the sequence can be represe

Find the nth term. Decide whether the sequence can be represented perfectly by a linear or a quadratic model, the model 0, 6, 16, 30, 48, 70, ...

0,6,16,30,48,70,..... is given so,
6-0=6
16-6=10
30-16=14
48-30=18
70-48=22
Please see that here our
first difference is 6,10,14,18,22......
now
10-6=4
14-10=4
18-14=4
22-18=4
and second difference is 4,4,4,4,...
which is same throughout
So, Its a quadratic equation