1.

If the sum of n terms of an A.P. is `3n^2+5`and its `m^(t h)`term is 164, find the value of m.

Answer» Here, we are given,
`n/2(2a+((n-1)d) = 3n^2+5n`
`(2a-d)+nd = 6n+10`
`d = 6 and 2a-d=10`
`d=6 and a =8`
Now, `m^(th)` term `= a+(m-1)d = 164`
`=>8+6(m-1) = 164`
`=>6(m-1) = 156`
`=> m = 27`


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