Final answer:
The function rule for the equation y = 21 - 3x is a linear function with a slope of -3 and a y-intercept of 21.
Step-by-step explanation:
The given equation in the problem is: Y=21-3x
The function rule for the is a linear function. In general, a linear function has the form y = mx + b, where m is the slope of the line and b is the y-intercept. In this case, the slope is -3 and the y-intercept is 21.
To find additional points to graph the line, you can choose different values of x and plug them into the equation to solve for y. For example, if x = 0, y = 21 - 3(0) = 21.
So one point on the graph is (0, 21). Similarly, if x = 1, y = 21 - 3(1) = 18. So another point on the graph is (1, 18).
You can continue to find more points or use the slope-intercept form of the equation to draw a straight line on a graph with the given slope and y-intercept.