Given, (2n + 4) / (5n + 5) = { 2a1 + (n-1) d1 } / { 2a2 + (n-1) d2 }
Putting n = 1, we get a2 = 5/3 a1 .....(1)
Putting n = 2 and n = 3, we get,
d1 = 2/5 d2 .....(2)
3/5 d2 = a1 ......(3)
So, we have the relations b/w a1, a2, d1 and d2. Hence, the ratio comes as 5/12