(1+5/x)^(3*x)
((1 + 5)/x)^(3*x)
(1 + 5/x)^(3*x)
3*x / 5\ lim |1 + -| x->oo\ x/
Limit((1 + 5/x)^(3*x), x, oo, dir='-')
15 e