Question

am i right?

A store displays six computers on a shelf side–by–side. If the first computer is eight inches wide and each successive computer is four inches wider than the previous one, find the total width of the computers on the shelf.

Part 1: Describe the sigma notation used in answering the question above. (2 points)

Part 2: Show all your work and answer the question. (3 points)

Answer 1

8
∑ 4 + 4n
n=1

∑ 4 + 4n = 4 ∑ 1 + n
4 * 8 + 4 ∑ n
32 + 4 [8 * 9 / 2]
32 + 40
72 inches

Answer 2

no, the answer is not

\[\Large \sum_{n=1}^{8}4+4n\]

for part 1


Part 2 depends on part 1, so that is also incorrect

Answer 3

ok can you help me then @jim_thompson5910

Answer 4

How many computers are we talking about here?

Answer 5

6

Answer 6

so you're not summing to 8 up at the top (of the sigma), you're summing to 6

Answer 7

thats the problem above says so i guess so

Answer 8

so it should be

\[\Large \sum_{n = 1}^{6}4+4n\]

for part 1

Answer 9

so is the first and 2nd part for part 2 right?

Answer 10

first part is, but the second is not...and you'd have to use 6 instead of 8

Answer 11

∑ 4 + 4n = 4 ∑ 1 + n
4 * 6 + 4 ∑ n
24 + 4 [6 * 7 / 2]
24 + 25
49 inches

Answer 12

?

Answer 13

4 [6 * 7 / 2]

doesn't become

25

Answer 14

84? i added thats why

Answer 15

108 inches ?

Answer 16

it is 108 inches

Answer 17

108 is the total final answer for part 2

Answer 18

can you help me with another problem?

Answer 19

sure, what is it

Answer 20

help me with the steps i have an answer just don't know how?
geometric partial sum ∑[i=1,5,3(-4)^(i-1)].

Answer 21

nevermind i found it

Answer 22

You're basically summing

3(-4)^(i-1)

from i = 1 to i = 5

So add up 3(-4)^(i-1) five times like so


3(-4)^(i-1)
3(-4)^(i-1)
3(-4)^(i-1)
3(-4)^(i-1)
3(-4)^(i-1)


Then replace the first i with 1, the second i with 2, the third with 3, etc etc like this

3(-4)^(1-1)
3(-4)^(2-1)
3(-4)^(3-1)
3(-4)^(4-1)
3(-4)^(5-1)

Now evaluate

Answer 23

but i do need help with What is the 5th partial sum of ∑[i=1,∞,-1+5n]

Answer 24

the answer i got for the last problem was 11,170

Answer 25

same thing, but you're now doing it with -1+5n

Answer 26

i got 60 ?

Answer 27

write out -1+5n five times

-1+5n
-1+5n
-1+5n
-1+5n
-1+5n

then replace the first n with 1, the second with 2, etc etc to get

-1+5(1)
-1+5(2)
-1+5(3)
-1+5(4)
-1+5(5)

Answer 28

Evaluate each piece, then add them all up

Answer 29

70?

Answer 30

yes, you are correct

the answer is 70