If k = {(x, y) | x - y = 5}, is set k a function?

Yes, set K is a function.

Step-by-step explanation:

Given K = {(x, y) | x - y = 5}

we have to find is above set is a function or not.

Functions are relations that give one output for each input, or one x- value gives only one value of y.

As, x-y=5

⇒ y=x-5

The above set is a function because every x-value produces a different y-value i.e K satisfies the definition of what it meant for a relation to be  function.

Hence, set K is a function.