#### Answer

not linear

#### Work Step by Step

A function is linear if there is a constant rate of change in the function, which is also called the slope.
Note that:
$\frac{1}{2}-\frac{1}{4}=\frac{1}{4}\\1-\frac{1}{2}=\frac{1}{2}\\2-1=1\\4-2=2$
The difference of consecutive $y$-values is not constant hence the function is not linear.