2-1

Could you clarify what you mean by “2-1”?

• If it’s the arithmetic, 2 − 1 = 1.
• If it’s exercise 2-1 in your homework/textbook, please paste the problem statement.
• If it’s Section 2.1 of a course (and you want a summary or practice problems), tell me the course name and topic.

Once you provide the problem or topic, I’ll give a step-by-step solution or a concise study guide with key concepts and practice questions.