Explain how you can tell if a function is a linear based on its equation

If a function is linear, that means the degree on the x variable is 1 when solved for y. This means that the exponent on the x is 1. For example:

y²=x

y=√x

y=x^1/2

This is not a linear function because the power on the x function is not 1

x+y=3

y=-x+3

This is a linear function because the exponent on the x is 1.

Any function where the x doesn't have an exponent present, or has an exponent of 1, is deemed a linear function.