1. The ratio of the sums of m and n terms of an AP is m2 : n2. show that the ratio of the mth and nth terms is (2m-1) : (2n-1)
  2. In an AP, the sum of first n terms is 3n2/2 + 5n/2, find its 25th term.

 

Let the first term and common difference of an A.P. is a, d respectively. So, sum of m and n terms of an A.P. is as,

And,

So,

Now,

Hence, ratio of mth and nth term is 2m-1 : 2n-1.

 

 

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