Hello, my name 's Lan. I'm a student in grade 7 . I go to school 6 days a week. I often walk to school. My classes start at 6:45 and finish at 11: 15. At school I learn about many things. My favorite subject is English. But I don't like Math because it's difficult. At recess, I usually chat with my friends, sometimes I play skipping rope or eat some snacks. I like to go fishing with my father after school.

1. What grade is Lan in ?

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2. How does she often go to school ?

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3. Does Lan never eat at recess ?

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4. What does Lan do after school ?

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Chứng minh rằng phương trình sau có 3 nghiệm phân biệt:

\(\frac{x-a}{b}+\frac{x-b}{a}=\frac{b}{x-a}+\frac{a}{x-b}\) (a, b là hằng, \(a\ne0,b\ne0,a\pm b\ne0\))