1 + 1 + 2 + 2 - 1
= ( 1 + 1 ) + 2 + 2 - 1
= 2 + 2 + 2 - 1
= ( 2 + 2 ) + 2 - 1
= 4 + 2 - 1
= ( 4 + 2 ) - 1
= 6 - 1
= 5
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1-1-1-1-1-1-1-1-1-1-1-1-+2-2-2-2-2-2-2-2+4+4-3-13+12345678
Tính?
1 + 1 …
1 + 2 …
2 + 2 …
1 + 1 …
2 + 1 …
1 + 3 …
3 + 1 …
1 + 2 …
3 + 1 …
1 + 1 …
1 + 3 …
2 + 1 …
Đọc tiếp
Tính?
| 1 + 1 =… | 1 + 2 =… | 2 + 2 = … | 1 + 1 =… |
| 2 + 1 =… | 1 + 3 =… | 3 + 1 =… | 1 + 2 =… |
| 3 + 1 =… | 1 + 1 =… | 1 + 3 =… | 2 + 1 =… |
Tính:
| 3 + 1 + 1 = … | 1 + 2 + 2 =… | 2 + 1 + 1 =… |
| 1 + 3 + 1 =… | 2 + 2 +1 =… | 2 + 1 + 2 =… |
Tính:
2 + 1 + 1 = 3 + 1 + 1 = 1 + 2 + 2 =
1 + 2 + 1 = 1 + 3 + 1 = 2 + 2 + 1 =
+, - ?
| 1… 2 = 3 | 2 … 1 = 3 | 1…1 = 2 | 1…4 = 5 |
| 3…1 = 2 | 3…2 = 1 | 2…1 = 1 | 2…2 = 4 |
frac{1}{2^2}+frac{1}{4^2}+frac{1}{6^2}+..+frac{1}{100^2}frac{1}{2^2}left(1+frac{1}{2^2}+frac{1}{3^2}+...+frac{1}{50^2}right)Có frac{1}{2^2} frac{1}{1.2}1-frac{1}{2} frac{1}{3^2} frac{1}{2.3}frac{1}{2}-frac{1}{3}....v........v............ frac{1}{50^2} frac{1}{49.50}frac{1}{49}-frac{1}{50}Cộng lại 1+frac{1}{2^2}+frac{1}{3^2}+...+frac{1}{50^2} 1+1-frac{1}{2}+frac{1}{2}-frac{1}{3}+...+frac{1}{49}-frac{1}{50}2-frac{1}{50}Rightarrow VT frac{1}{2^2}left(2-frac{1}{50}right)frac{1}{2...
Đọc tiếp
\(\frac{1}{2^2}+\frac{1}{4^2}+\frac{1}{6^2}+..+\frac{1}{100^2}=\frac{1}{2^2}\left(1+\frac{1}{2^2}+\frac{1}{3^2}+...+\frac{1}{50^2}\right)\)
Có \(\frac{1}{2^2}< \frac{1}{1.2}=1-\frac{1}{2}\) \(\frac{1}{3^2}< \frac{1}{2.3}=\frac{1}{2}-\frac{1}{3}\)....v........v............ \(\frac{1}{50^2}< \frac{1}{49.50}=\frac{1}{49}-\frac{1}{50}\)
Cộng lại \(1+\frac{1}{2^2}+\frac{1}{3^2}+...+\frac{1}{50^2}< 1+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{49}-\frac{1}{50}=2-\frac{1}{50}\)
\(\Rightarrow VT< \frac{1}{2^2}\left(2-\frac{1}{50}\right)=\frac{1}{2}-\frac{1}{2^2.50}< \frac{1}{2}\left(Đpcm\right)\)