Question

What least number of terms of the sequence 17, `15 4/5 , 14 3/5 `should be taken so the sum is negative.

Answer 1

`S_n=n/2(2a+(n-1)d)`
`=n/2((a+l)/2)`
`s_n<0`<br> `(a+l)/2<0`<br> `2a+(n-1)d<0`<br> `2aL-(n-1)d`
`2aL-(n-1)d`
`34L-(n-1)-6/5`
`170/6<+(n-1)`<br> `170/6+1L.`
`29.33 `n=30`