If 3+5+7+...+to n terms/5+8+11+...to 10 terms =7,then the value of n is
Answers
Answered by
4
[tex]for \: the \: series \\ 3 + 5 + 7.....n \\ a = 3 \: and \: d = 2 \\ sn = \frac{n}{2}(2a - d + nd) \\ \frac{n}{2}(4 + 2n).....1 \\ for \: the \: series \: \\ 5 + 8 + 11.....n \\ a = 5and \: d = 3 \\ sn = \frac{n}{2} (7 + 3n) .....2\\
and for n=10
5(7+30) = 185
and
n(2+n)/185=7
n^2+2n=1295
and for n=10
5(7+30) = 185
and
n(2+n)/185=7
n^2+2n=1295
Similar questions