Khan/khan-exercises

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 Arithmetic sequences 1
randRange(-10, 10) randRangeNonZero(-6, 6) randRange(3, 5) _.map(_.range(N), function(i) { return A + i * D; })

The first cardinalThrough20(N) terms of an arithmetic sequence are given:

GIVEN.join(","), \ldots

What is the ordinalThrough20(N + 1) term in the sequence?

A + D * N

In any arithmetic sequence, each term is equal to the previous term plus the common difference.

Thus, the second term is equal to the first term plus the common difference. In this sequence, the second term, A + D, is abs(D) more than the first term, A.

Thus, the second term is equal to the first term plus the common difference. In this sequence, the second term, A + D, is abs(D) less than the first term, A.

Therefore, the common difference is D.

The ordinalThrough20(N + 1) term in the sequence is equal to the ordinalThrough20(N) term plus the common difference, or A + D * (N - 1) + D = A + D * N.

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