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ta có \(\left(n^2-n+1\right)+\left(n^2+n+1\right)\\ =n^2-n+1+n^2+n+1\\ =2n^2+2\)
=>\(n\in\left\{n\in N\right\}112\le n\ge123\)
bài này mk k bt cách trình bày nhưng kết quả hình như là 15 đó bạn....
Điền vào mỗi chỗ trống một từ thích hợp
My name is Lan. I study at a middle school in Ha Noi. I usually get up at half past five in the morning. I have breakfast at a quarter past six and go to school at half past six. I study nine subjects: Literature, Math, History, geography, Civics, English,Physics, Biology, and Physical Education. I have Math, English and History on Monday. Math and English are my favourite subjects. I think they are very interesting. In the afternoon, we stay at school and have more exercises for all subjects. We also play football or volleyball in the school yard. We sometimes go to the school library to read books
My name is Lan. I study at a middle school in Ha Noi. I usually get up at half past five in the morning. I have breakfast at a quarter past six and go to school at half past six. I study nine subjects: Literature, Math, History, geography, Civics, English,Physics, Biology, and Physical Education. I have Math, English and History on Monday. Math and English are my favourite subjects. I think they are very interesting. In the afternoon, we stay at school andhave more exercises for all subjects. We also play football or volleyball in the school yard. We sometimes go to the school library to read books
3x=5y
=>x/5=y/3
=>2x/10=3y/9=2x-3y/10-9=5/1=5(tính chất dãy tỉ số bằng nhau)
\(A=2+4+6+...+100\)
\(B=1+3+5+...+99\)
\(C=A-B=2-1+4-3+...+100-99\)
\(C=1+1+...+1=50\)