Question

the eighth term in an arithmetic sequence is 5, and the sum of the first 10 terms is 20. find the common difference and the first term of the sequence.

Answer 1

a=-3.4, d=1.2

Explanation:

we have to form two simultaneous equations.

a+7d=5 -> 2a+14d=10

10/2[2a+9d]=20 -> 2a+9d=4

and so

5d=6, d=1.2

a=-3.4