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Malatalorea8go
Answered

what is the sum of first 20 terms of an arithmetic sequence 3 7 11 15 19​

Sagot :

Zhairavvillanogo

S=n/2(2a+ (n-1)d)

=20/2(2×3+(20-1)×4)

=10(6+19×4)

=10(6+76)

=10(82)

=820

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