After you get the title, first look at the title and understand its meaning. In the topic, suppose that the number of cube A facing upwards is represented by X, and the number of cube B facing upwards is represented by Y, and make a tree diagram. First, draw six possibilities of X (there is a number of cube facing upwards), namely the numbers 1, 2, 3, 4, 5 and 6.
Suppose that the number of cube A facing upwards is 1, that is, x= 1, and list six possibilities of y (the number of cube B facing upwards). Assuming that the number of A cubes facing up is 2, that is, x=2, six possibilities of Y (the number of B cubes facing up) are listed.
By analogy, when x=3, x=4, x=5, x=6, six possibilities of y (the number with the small cube of b facing upwards) are listed respectively. Get the picture below. And from the tree diagram drawn, it can be concluded that there are 36 possibilities for point P(x, y)***.
Among these 36 possibilities, we can find the point p that falls on the image of the function y=-2x+9. There are three, namely (2,5), (3,3) and (4, 1). It can be calculated that the probability that point P falls on the image of function y=-2x+9 is112, which is one twelfth.
Take shooting as an example. If you shoot n times, what is the probability of hitting …? Draw two branches to represent the first pitch: alto and alto. Next, in the second shot, draw two branches from the middle and missed branches respectively, and there will be four results: middle and missed; Yes, no. By analogy, we can get a tree diagram, from which we can see the probability of each situation.