Question
Mathematics Question on Sequences and Series
Find the 20th term of the series 2×4+4×6+6×8+ ... + n terms.
Answer
The given series is 2 x 4 + 4 x 6 + 6 x 8 + … n terms
∴ n th term = an = 2n x (2n + 2) = 4n 2 + 4n
a20 = 4 (20)2 + 4(20) = 4 (400) + 80 = 1600 + 80 = 1680
Thus, the 20th term of the series is 1680.