Explanation:
a linear function is defined as
y = ax + b
the variable x is only occurring with the exponent of 1.
this represents a straight line in a graphic representation (hence the name "linear").
if the exponent of the variable x is not 1, then it is not a linear function
P : y = 3/x + 2³
it is not linear.
the exponent of x = -1, as 1/x = x^-1. -1 is different to 1, which would be needed as exponent of x to make it linear.
Q : y = (1/3)x² + 3
it is not linear.
the exponent of x = 2. and 2 is different to 1, which would be needed as exponent of x to make it linear.