13. If the sum of n terms of an A.P. is and its term is 164, find the value of m.
Given : If the sum of n terms of an A.P. is and its term is 164
Let a and d be first term and common difference of a AP ,respectively.
Sum of n terms =
Comparing the coefficients of n on both side , we have
m th term is 164.
Hence, the value of m is 27.