If only one element of "A" points to one element of "B", then the elements of "B" can point to the elements of "A" in turn. But if it is like being in a "general function".
There can be multiple "A" elements pointing to the same "B" element, and this "B" element cannot point to an "A" element in turn. Read the inverse function for more information.
Single-handedness is also called "one-on-one".
A surjection means that every (all) element of "B" has at least one relative element of "A" (maybe more than one), and none of the elements of "B" has a relative element of "A".
The duality means that injectivity and injectivity are both established, so there is a perfect "one-to-one" relationship between each element of two sets (but this is not just a "one-to-one" relationship of injectivity).
Ways to learn mathematics well:
1, prepare well before class and take the initiative in class. The quality of preparation before class directly affects the effect of listening to lectures.
2. Listen carefully in class and take notes.
3. Review in time and turn knowledge into skills.
4. Seriously finish homework, form skills and skills, and improve the ability to analyze and solve problems.
5. Summarize in time and systematize what you have learned.