Question

Sigma Notation Help?

Answer 1

Given the sequence 9, 12, 15, which of the following is equivalent to

Answer 2

54
102
144
162

Answer 3

Okay, so the way to read that is that it is "the sum from n=5 to n=8 of An."
So you start at 5, go up by 1 each time and stop at 8. For each one of those, you should add in what is in the middle. In this case, the middle is An, which means to do the nth term so the sequence.

So this gives you
\[\Large a_5 + a_6 +a_7 + a_8\]
Which means
(The fifth term) + (the sixth term) + (the seventh term) + (the eighth term)

Answer 4

Does that much make sense to you? Ask me questions.

Answer 5

Right... and the formula to solve for an is:
an=a1+(n-1)d
an=(9)+(n-1)(3)
an=9+3n-3
an=6+3n

I see. Thank You!

Answer 6

Very good =)

Answer 7

Thanks again!

Answer 8

My pleasure! =D