To solve the exercise you can graph and join the ordered pairs that make up each function. The function whose graph is a straight line will be a linear function. So, you have:
First function:
As you can see the points form a straight line, so this function is linear.
Second function:
As you can see, the points do not form a straight line, so this function is not linear.
Third function:
In this case, they give you the equation of a line in its slope-intercept form, that is:
[tex]\begin{gathered} y=mx+b \\ \text{ Where m is the slope of the line and } \\ \text{b is the y-intercept} \end{gathered}[/tex]
So this function of course is linear and the graph of this would be:
Fourth function:
This function is called absolute value and it determines the distance from a number to zero. Its graph is:
As you can see, the graph of this function is not totally a single line, so this function is not linear.
