## anonymous one year ago HELP! with summation notation. will medal! (see attachment)

1. anonymous

2. anonymous

3. anonymous

Do you need to find the sum?

4. anonymous

yes @Nixy

5. anonymous

The first one is arithmetic so we can do the following First find the first and last terms by putting n= 1 and n = 50 $$\huge a_1 = 3(1) + 7 = 10$$ 10 is your first. Now find the last $$\huge a_1 = 3(50) + 7 = 157$$ Ok, next part coming. I am doing number 6

6. anonymous

Do you still need help?

7. anonymous

Now we use the formula $$\huge S_n = \frac{n}{2}(a_1+a_n)$$ Now just plugin our numbers $$\huge S_{50} = \frac{50}{2}(10+157)$$ $$\huge S_{50} = 4175$$

8. anonymous

is that the answer?? thats how you do it? @Nixy

9. anonymous

That is all the steps and the answer is 4175

10. anonymous

could you also help with 7? then ill do 8 and 9 by my self @Nixy

11. anonymous

12. anonymous

Number 7 looks like the Sum of an Infinite Geometric Series

13. anonymous

if i do it will you check it?

14. anonymous

actually i have number 7 done but I dont understand 8

15. anonymous

i dont get how there is no number above the "e"

16. anonymous

@Nixy

17. anonymous

$$\huge \sum_{n=1}^{12} 2*4^n$$ First you need to rewrite the series so it is in the form of $$\huge \sum_{n=1}^{12} a_1*r^{n-1}$$ $$\huge \sum_{n=1}^{12} 8*4^{n-1}$$ Now identify a_1 and r ? If |r| < 1 the series is converges and we need to find the sum if not it, there is no need to find the sum Sorry I am at work and that is why it is taking me a little bit of time.

18. anonymous

is this number 8? @Nixy