Answer:
Exponential
Step-by-step explanation:
For this question you need to understand what is a linear function and what is an exponential function.
Linear function is a function where any variable x,y,z has the power of maximum 1 for example
x+y=1
7x+2y=10
1000x+9999y=40000
The numbers look too big but its the same category as linear function because all the variable in the equation are to the power of 1
Whereas, An exponential function is a mathematical function of the following form: [tex]y=a^x[/tex] where x is a variable, and a is a constant called the base of the function. Most commonly exponential functions are involved with mathematical symbol [tex]e[/tex].
So in your question [tex]y=4.2^x[/tex] where x the variable has become the power/degree the fucntion is an exponential function.