Multiple choice

If the first term of an arithmetic sequence is $-14$ and the common difference is $2$, find the sum of the first $8$ terms.

  1. $-56$
  2. $-46$
  3. $-36$
  4. $-26$
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A Correct answer
Explanation

Sum of n terms = n/2 * (2a + (n-1)d). n=8, a=-14, d=2. Sum = 8/2 * (2*(-14) + 7*2) = 4 * (-28 + 14) = 4 * (-14) = -56.

AI explanation

Use the arithmetic series sum formula Sn = n/2 * (2a + (n-1)d). The first term a is -14, the common difference d is 2, and the number of terms n is 8. Substituting these values gives S8 = 8/2 * (2*(-14) + (8-1)*2) = 4 * (-28 + 14) = 4 * (-14) = -56.

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