Question

Write the sum using summation notation, assuming the suggested pattern continues. (7 points)

2 - 6 + 18 - 54 + ...

Answer 1

These are the answer choices

Answer 2

@peachpi any ideas?

Answer 3

It looks like each terms is the one before it multiplied by a specific number. What do you think the number is?

Answer 4

2?

Answer 5

Well 2 is the first number, the a1. What do you multiply 2 by to get -6?

Answer 6

-3

Answer 7

right, so -3 is r and 2 is a1. and this is a geometric series because of the multiplication. The form is\[\sum_{n=0}^{\infty}a _{1}(r) ^{n-1}\]

Answer 8

Oh okay so it's a

Answer 9

hold up

Answer 10

it's d. I made a mistake in the formula. The exponent is just n

Answer 11

oh I see