12. Rumus suku ke-n barisan bilangan 2/5, 3/7, 4/9, 5/11adalah​

Jawab:

perhatikan :

U1 = 2/5 = (1 + 1)/(2(1) + 3)

U2 = 3/7 = (2 + 1)/(2(2) + 3)

U3 = 4/9 = (3 + 1)/(2(3) + 3)

U4 = 5/11 = (4 + 1)/(2(4) + 3)

…..

maka

Un = (n + 1)/(2n + 3)