Final answer:
The function y = 6 + 9 is linear because it represents a straight line with a constant slope and no curving or bending.
Step-by-step explanation:
The function y = 6 + 9 is linear.
In a linear function, the graph is a straight line. It has a constant slope, which means that for every increase of 1 in the x-coordinate, the y-coordinate increases by the same amount. In this case, the slope is 0, so the line is horizontal. The value 6 is the y-intercept, which is the point where the line intersects the y-axis. The line does not curve or bend, making it a linear function.