Answer: Yes, this is a linear function between P and M.
Explanation:
We can define a function as a relation between two or more variables, like y = f(x).
This function, maps the elements x (the input) into elements y (the output).
We have a rule for a function: Each input x can be mapped into only one output y.
In this case, we have:
P = 0.15*M + 20.
Let's prove that each value of M is related to only one value of P.
Suppose that, for a given M0, we have:
0.15*M0 + 20 = p1
and also for M0, we have:
0.15*M0 + 20 = p2
This means that p1 = p2, so we can not have different outputs for the same input.
This is a linear relation, so each value of M is related to only one value of P.
Then this is a function P(m) = 0.15*M + 20.