Arithmetic Question. Question in comments.

Question

rhondasommer · Answer

attachment

rhondasommer · Answer

I just need help with D?

rhondasommer · Answer

@tkhunny

phi · Answer

you should fix part c

I think they want  
$$ a_n =  a_1 + (n-1) d $$
for the first part of C  (but with your a1 and your d)

orange_ · Answer

Yep, was just going to say that.

rhondasommer · Answer

oh im so confused? It says use sigma?

phi · Answer

the 2nd part is to use the sigma notation

rhondasommer · Answer

so, I had the second part right? or just none?

phi · Answer

the 2nd part is not correct because you have it "saying"
add up 5, 6, 7... 

you should add up
$$ a_n= 4 + (n-1)\cdot 4 $$

phi · Answer

if you know algebra, you can simplify
$$ a_n= 4+ 4(n-1) \ = 4+4n - 4 \= 4n$$
and that is what you add up (for n=1 to 10)

rhondasommer · Answer

oh... so? i guess im confused as to what my answer should be them?

what am I changing? 

and what is part D?