For a given arithmetic sequence, and . Find

a) the common difference.

b) .

Answers: a) -1, b) 0

Could someone explain to me the method?

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- Apr 3rd 2010, 02:04 PMshawliAnother arithmetic sequence problem
For a given arithmetic sequence, and . Find

a) the common difference.

b) .

Answers: a) -1, b) 0

Could someone explain to me the method? - Apr 3rd 2010, 04:38 PMsatx
I would think that Un + m would equal 2m since Un = m. Could you explain why that is not the case?

- Apr 3rd 2010, 04:45 PMSoroban
Hello, shawli!

You typed part (b) incorrectly . . .

Quote:

For a given arithmetic sequence: .

Find: .

. . . . .

Answers: .

We have: .

Equate [1] and [2]: .

. . . . . .

If , we have: .

. . and the arithmetic sequence cannot be determined.

If , then: .

. . . .

Since , we have: .