Question

Find the sum of the geometric sequence if the first term is -8, the common ratio is -3 and there are 10 terms

Answer 1

Explanation:

The sum of a geometric sequence can be found using the formula

Sn = a₁ (1 - rⁿ⁻¹)/ (1 - r)

where a₁ is the first term, r is the common ratio, and n is the number of terms.

In this case, a₁ = -8, r = -3, and n = 10.

Plugging these values into the formula, we get

Sn = -8 (1 - (-3)⁹⁻¹) / (1 - (-3))

Sn = -8 (1 + 3⁹) / 4

Sn = -8 (1 + 19683) / 4

Sn = -8 × 19684 / 4

Sn = -4920