First, let's look at y=15.
If you graph this, this is just a horizontal line with a y value of 15.
Thus, the first function is linear.
Next, let's look at
Notice that this function has an x to a power of 3.
Since this power is greater than 1, this cannot be linear.
Thus, the second function is nonlinear.
Finally, let's look at y=11+5x.
Let's change the order of the 11 and 5x.
We get y=5x+11.
This function is in the form of y=mx+b, which is the slope-intercept form of a line (where m is the slope and b is the y-intercept).
Thus, the last function is linear.
