The equation "y = 2x + 5" can be written as a statement that a proposition P(n) is true for all integers n. 

In mathematics, a proposition P(n) is a statement that is either true or false.

In mathematics, a proposition P(n) will always be proven true.

The statement "All odd numbers are prime" can be written as a statement that a proposition  P(n) is true for all integers n.