Given
![16x-y^4=0 \\ \\ \Rightarrow y^4=16x \\ \\ \Rightarrow y= \sqrt[4]{16x} =2 \sqrt[4]{x}](https://img.qammunity.org/2018/formulas/mathematics/high-school/s1t7wiucd7le5wk541wxd5dm8ur4joi3cf.png)
For any value of x, there are two possible values of y, thus the equation does not represent y as a function of x.
A
function is a relation between a set of inputs and a set of permissible outputs with the property that each input is related to exactly one output.