A sequence is defined by a_{n + 1} = a_n + 2n, and a_1 = 4. What is the sum of the seventh term and eighth term?
A sequence is defined by a_{n + 1} = a_n + 2n, and a_1 = 4.
This recursion can be written as: an = a1 + (n-1)*n
You can easily obtain a7 + a8 from this.
