QUESTION: Find a counter-example for each of the statements below:

1. Every month of the year has 30 or 31 days.

2. If n is an integer and n² is divisible by 4, then n is divisible by 4.

3. For every positive integer x, x³ < 2^x

4. Every positive integer can be expressed as the sum of the squares of two integers.

5. The multiplicative inverse of a real number x, is a real number y such that xy = 1. Every real number has a multiplicative inverse..