## anonymous one year ago Write the sum using summation notation, assuming the suggested pattern continues. $$-9-3+3+9+...+81$$

1. Michele_Laino

we have an arithmetic sequence, whose firs term is -9, and the constant is: d= -3-(-9)=3-(-3)=...

2. anonymous

Would it be $\huge \sum_{n=0}^{\infty}=(-9+6n)$ because the common difference is 6?

3. anonymous

Wait, it should 15 not infinity. :D

4. geerky42

That's correct.