Question

the sum of first n terms of an arithmetic sequence is n square +2n.
a) what is the first term?
b)find the common difference
c)what is the sum of the first 20 term of this sequence
d)prove that the sum of continuous terms starting from the first of the sequence 3, 5, 7, added to 1 gives a perfect square​

Answer 1

Step-by-step explanation:

refer to the attachment above