Question

Write the sum using summation notation, assuming the suggested pattern continues.

-9 - 3 + 3 + 9 + ... + 81

Could someone please help?? I will medal, but I just don't understand these problems.

Answer 1

Hint: Write the numbers as exponents.

Answer 2

So...
-3^2 - 3^1 + 3^1 + 3^2 ...

Answer 3

@Hero

Answer 4

Yes

Answer 5

Write 81 as an exponent

Answer 6

9^2 or 3^4 ? @Hero

Answer 7

Think about it.

Answer 8

Yes, it is 3^4, so in total:

-3^2 - 3^1 + 3^1 + 3^2 ... 3^4

Answer 9

@Hero

Answer 10

Good. What number exists between 3^2 and 3^4?

Answer 11

3^3

Answer 12

Exactly. So now you can write using summation notation since you have the complete pattern.

Answer 13

I'm confused on how to write it into summation notation.

Answer 14

Do you know what summation notation looks like?

Answer 15

Yes, I do.

Answer 16

Well, then you should try your best to write the pattern in summation notation. Don't be afraid to make a mistake.

Answer 17

Ok I'll give it a try. Thanks!