MathRevolution wrote:

[GMAT math practice question]

The terms of the sequence {An} satisfy A2 - A1 = 2, A3 - A2 = 5 and A4 - A3 = 10. Which of the following could be the formula for An+1 - An, in terms of n?

\(A. n + 1\)

\(B. n^2 + 1\)

\(C. n^2 - 1\)

\(D. n - 1\)

\(E. n^2 + 3\)

Let n=3.

According to the blue portion above, A

n+1 - A

n = A

4 - A

3 = 10.

The correct answer must yield a result of 10 when n=3.

Only B works:

n² + 1 = 3² + 1 = 10.

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