Question

the sum of first 21 terms of an arthimrtic sequence is 735.find its 11th term​

Answer 1

Answer:

SN+SN=

={[a]+[a+(N−1)d]}+

+{[a+d]+[a+(N−2)d]}+...

... +{[a+(N−2)d]+[a+d]}+

+{[a+(N−1)d]+[a]}