The first term is 3 and the common difference is negative 3. Then the sum of the first 20 terms will be negative 510.
What is a series?
A series is a sum of sequence terms. That is, it is a list of numbers with adding operations between them.
The first term (a₁) = 3 and the common difference (d) = -3. Then the sum of the first 20 terms will be
Sₓ = (x/2) [2a₁ + (x - 1)d]
Then we have
S₂₀ = (20/2) [2 × 3 + (20 - 1)-3]
S₂₀ = 10 [6 + (19)(-3)]
S₂₀ = 10 [6 - 57]
S₂₀ = 10 [51]
S₂₀ = -510
More about the series link is given below.
https://brainly.com/question/10813422
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