## anonymous one year ago Evaluate

1. anonymous

|dw:1439771083905:dw| I got -385 :)

2. jim_thompson5910

I'm getting the same answer. Nice work.

3. tkhunny

$$\sum_{n=3}^{12}(-5n-1) = -\sum_{n=3}^{12}(5n+1) = -10 - \sum_{n=3}^{12}(5n)= -10 - 5\sum_{n=3}^{12}n$$ Is it getting easier? Your result is good. Think about different ways to approach it.

4. anonymous

Thanks :)