2-9

Do you mean one of these?

• Arithmetic: 2 − 9 = −7.
• Exercise 2.9 from a textbook: please paste the full problem statement so I can solve it step by step.
• Problems 2–9 in a section: tell me the topic (e.g., solving equations, derivatives, etc.) and I can help you prepare a targeted study plan or generate practice questions.

If you share the exact problem, I’ll work through it now.