U0 = 48
U1 = (3/4)U0 + 25
U2 = (3/4)U1 + 25 = (3/4)2U0 + 25(1 + 3/4)
U3 = (3/4)U2 + 25 = (3/4)3U0 + 25(1 + 3/4 + (3/4)2)
...
Un = (3/4)nU0 + 25(1 + 3/4 + (3/4)2 + ... + (3/4)n-1)
As n tends to infinity (3/4)n tends to 0 and the sum in brackets tends to 1/(1 - 3/4) = 4, so Un tends to 25*4 = 100
U0 = 48
U1 = (3/4)U0 + 25
U2 = (3/4)U1 + 25 = (3/4)2U0 + 25(1 + 3/4)
U3 = (3/4)U2 + 25 = (3/4)3U0 + 25(1 + 3/4 + (3/4)2)
...
Un = (3/4)nU0 + 25(1 + 3/4 + (3/4)2 + ... + (3/4)n-1)
As n tends to infinity (3/4)n tends to 0 and the sum in brackets tends to 1/(1 - 3/4) = 4, so Un tends to 25*4 = 100