Nguyễn Khắc Huy Hoàng
Giới thiệu về bản thân
S=(2⋅1)2+(2⋅2)2+…+(2⋅50)2cap S equals open paren 2 center dot 1 close paren squared plus open paren 2 center dot 2 close paren squared plus … plus open paren 2 center dot 50 close paren squared𝑆=(2⋅1)2+(2⋅2)2+…+(2⋅50)2Dãy này bao gồm 50 số hạng. Bằng cách đưa thừa số chung 22=42 squared equals 422=4 ra ngoài, ta được:
S=4⋅(12+22+…+502)cap S equals 4 center dot open paren 1 squared plus 2 squared plus … plus 50 squared close paren𝑆=4⋅(12+22+…+502) Tiếp theo, ta sử dụng công thức tính tổng nn𝑛 số chính phương đầu tiên:
.
Áp dụng công thức này với , ta tính được tổng trong ngoặc:
Cuối cùng, ta thay giá trị này trở lại biểu thức của và tính toán kết quả cuối cùng:
Rút gọn cho ta được :
Vậy, tổng của dãy số là 171700.
trắc chứ vậy tôi sẽ trả lời
My best friend's name is Linh. She is a very kind and caring person. We met in high school and have been close ever since. Linh is always there for me, offering support and a listening ear, whether I am happy or sad. She has a great sense of humor and can always make me laugh. We enjoy spending time together, often just talking or listening to music. I am very grateful to have such an amazing and loyal friend in my life, and I hope our friendship lasts forever.
12 345:2=6,1725
My best friend's name is Linh. She is a very kind and caring person. We met in high school and have been close ever since. Linh is always there for me, offering support and a listening ear, whether I am happy or sad. She has a great sense of humor and can always make me laugh. We enjoy spending time together, often just talking or listening to music. I am very grateful to have such an amazing and loyal friend in my life, and I hope our friendship lasts forever.
1+2+3+4+5+6+7+8+9+10
=(1+9)+(2+8)+(3+7)+(4+6)+(5+10)
=10+10+10+10+15
=20+10+10+15
=30+10+15
=40+15
=55
My best friend's name is ................ He/She is a very kind and caring person. We met in high school and have been close ever since. He/she is always there for me, offering support and a listening ear, whether I am happy or sad. He/She has a great sense of humor and can always make me laugh. We enjoy spending time together, often just talking or listening to music. I am very grateful to have such an amazing and loyal friend in my life, and I hope our friendship lasts forever.
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