## anonymous one year ago @hartnn Write the sum using summation notation, assuming the suggested pattern continues. 5 - 15 + 45 - 135 + ...

1. hartnn

do you see any pattern in that?? like if you multiply/divide current term with a certain number, you get the next term??

2. anonymous

the cerrent term multiplied by 3

3. hartnn

if you multiply it by just a 3, then you will get all positive numbers, try multiplying by -3!

4. anonymous

so $\sum_{n=0}^{\infty}5(-3)^n$

5. anonymous

?

6. hartnn

so, using a summation notation in general, $$\Large \sum \limits_{n=0}^{n=\infty } f(n)$$ oh you already got it!

7. anonymous

ok thanks!

8. hartnn

yes thats correct :)