How many different 4 digit numbers are there that are only made up of even digits

In a four-digit number, the first digit cannot be 0, so there are only 4 even numbers available. For the second, third, and fourth digits, there are 5 available numbers. Thus, the number of 4-digit numbers containing only even digits is 4 x 5 x 5 x 5 = 500 numbers.

(1/x + 1)^2 + 6 (1/x + 1) +5