Find the 20th term of the series 2 × 4 + 4 × 6 + 6 × 8 + … + n terms.
The given series is 2 × 4 + 4 × 6 + 6 × 8 + … n terms
∴ nth term = an = 2n × (2n + 2) = 4n2 + 4n
a20 = 4 (20)2 + 4(20) = 4 (400) + 80 = 1600 + 80 = 1680
Thus, the 20th term of the series is 1680.