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

Answer

N/a

Explanation

`"Here "S_(n)=3n^(2)+5n`
`rArr" "S_(m)=3m^(2)+5m`
`"and "S_(m-1)=3(m-1)^(2)+5(m-1)`
`"Now "T_(m)=S_(m)-S_(m-1)`
`rArr" "T_(m)=3m^(2)+5m-3(m-1)^(2)-5(m-1)=3(2m-1)+5=6m+2`
Now, according to the problem, `T_(m)=164`
`rArr" "6m+2=164`
`rArr" "6m=164 rArrm=27`