Question

Find the first four terms of the sequence given a1​=−9 and an+1​=an​+n.

A. -9, -5, 0, 6
B. -9, -8, -6, -3
C. -9, -10, -12, -15
D. -9, -6, -2, 3

Answer 1

The first four terms of the given sequence, starting with a1 = -9 and an+1 = an + n, are -9, -8, -6, -3.

Step-by-step explanation:

The given sequence starts with a1 = -9 and each subsequent term, an+1, is obtained by adding n to the previous term, an.

By substituting the values and finding the pattern, we can calculate the first four terms of the sequence as follows:

1. a1 = -9
2. a2 = a1 + 1 = -9 + 1 = -8
3. a3 = a2 + 2 = -8 + 2 = -6
4. a4 = a3 + 3 = -6 + 3 = -3

Therefore, the first four terms of the sequence are -9, -8, -6, -3, which corresponds to option D.