Finding Nth term of a Quadratic sequence

A sequence is a collection of terms arranged in a specific order, where
each term is obtained according to a rule.
In a quadratic sequence The row of 1st differences is not constant, and so the rule for the nth is linear and takes the form Tn = an + b.
By substituting the values of n into the rule, each term can be written in
terms of a and b.The row of 2nd differences is constant, and so the rule for the nth term is therefore a quadratic which takes the form Tn = an2 + bn + c.
By substituting the values of n into the rule, each term can be written in
terms of a, b and c.