Determine if Linear f(x)=6x^4

The word linear is used for a straight line. A linear function is a function of a straight line, which means that the degree of a linear function must be ${\displaystyle 0}$ or ${\displaystyle 1}$. In this case, The degree of ${\displaystyle f\left(x\right)=6x^4}$ is ${\displaystyle 4}$, which makes the function a nonlinear function.