If f (lgx) = 1 + 2 / x + X, then f (1)=

In the first method, as mentioned above, f (1) is equivalent to the value of (1 + x) / (2 + x) when f (lgx) x = 10, i.e. 12 / 11
It can also be directly substituted back to get the explicit expression of F: y = > lgx: x = 10 ^ y: F (lgx) = f (y) = (2 + 10 ^ y) / (1 + 10 ^ y), substituting f (1) = 12 / 11