Question

find the sum of the first n terms of the series 1.3+3.5+5.7

Answer 1

Answer:

your answer is 10.5

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Answer 2

SOLUTION

The nth term of the series will be n(n+2)

The sum upto nth terms= ∑n(n+2)

=) ∑n^2 +2n

=) ∑n^2+ 2∑n

=) n(n+1)(2n+1)/6+2n(n+1)/2

=) n(n+1)(2n+1)/6+n(n+1)

=) n(n+1)[2n+1/6+1]

=) n(n+1)[2n+7/6]

=) n(n+1)(2n+7)/6

Hope it helps ☺️