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tretraunamsach
2 năm trước
Ví dụ: 2 + 4 + 6 + 8 + ... + 100 Giải: Số các số hạng của tổng là: (100 – 2) : 2 + 1 = 50 (số hạng) Tổng đã cho bằng: (2 + 100). 50 : 2 = 2550 Vậy 2 + 4 + 6 + 8 + ... + 100 = 2550 Bài tập vận dụng 2 + 4 + 6 + 8 + ... + x = 10 302. Tìm x 1 + 4 + 7 + 10 + ... + y = 1717. Tìm y Làm cách lớp 5 nha
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