In order to determine the value of f(x) as x approaches to oo, replace larger values of x into the function and identify the tendency of f(x), as follow:
x = 1000
[tex]f(1000)=(1+\frac{1}{1000})^{1000}\approx2.7169[/tex]x = 1000000
[tex]f(1000000)=(1+\frac{1}{1000000})^{1000000}\approx2.7182[/tex]x=1000000000
[tex]f(1000000000)=(1+\frac{1}{1000000000})^{1000000000}\approx2.7182[/tex]As you can notice, as x approaches to oo, f(x) approaches to 2.7182..., which is the value of constant e.
answer: e