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Kết quả làm tròn số 89, 3216 đến số thập phân thứ 3 là:
A. 89, 321. B. 89, 322. C. 89, 324 D. 89, 326
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\(\Leftrightarrow\frac{x-5}{325}-1+\frac{x-6}{324}-1=\frac{x-7}{323}-1+\frac{x-8}{322}-1\)
\(\Leftrightarrow\frac{x-330}{325}+\frac{x-330}{324}-\frac{x-330}{323}-\frac{x-330}{322}=0\)
\(\Leftrightarrow\left(x-330\right)\left(\frac{1}{325}+\frac{1}{324}-\frac{1}{323}-\frac{1}{322}\right)=0\)
Ma \(\frac{1}{325}+\frac{1}{324}-\frac{1}{323}-\frac{1}{322}\ne0\)
\(\Rightarrow x-330=0\)
\(\Rightarrow x=330\)
\(\frac{x-5}{325}+\frac{x-6}{324}=\frac{x-7}{323}+\frac{x-8}{322}\)
\(\Leftrightarrow\left[\frac{x-5}{325}-1\right]+\left[\frac{x-6}{324}-1\right]=\left[\frac{x-7}{323}-1\right]+\left[\frac{x-8}{322}-1\right]\)
\(\Leftrightarrow\frac{x-5-325}{325}+\frac{x-6-324}{324}=\frac{x-7-323}{323}+\frac{x-8-322}{322}\)
\(\Leftrightarrow\frac{x-330}{325}+\frac{x-330}{324}=\frac{x-330}{324}+\frac{x-330}{332}\)
\(\Leftrightarrow\frac{x-330}{325}+\frac{x-330}{324}=\frac{x-330}{324}+\frac{x-330}{332}=0\)
Auto làm nốt :v
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ta có n3\(\equiv\)0(mod n)
=> n3-1\(\equiv\)-1(mod n)
=>( n3-1)111\(\equiv\)-1(mod n)
Ta lại có
n2\(\equiv\)0(mod n)
=> n2-1\(\equiv\)-1(mod n)
=>( n2-1)333\(\equiv\)-1(mod n)
vậy số dư khi chia (n3-1)111.( n2-1)333 cho n là 1
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\(\hept{\begin{cases}n^3-1\equiv-1\left(mod\text{ }n\right)\\n^2-1\equiv-1\left(mod\text{ }n\right)\end{cases}}\Rightarrow\left(n^3-1\right)^{111}.\left(n^2-1\right)^{333}\equiv\left(-1\right)^{111}.\left(-1\right)^{333}\equiv\left(-1\right).\left(-1\right)\equiv1\)\(\left(mod\text{ }n\right)\)
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C = 3 - 32 + 33 - 34 + 35 - 36 +...+ 323 - 324
3C = 32 - 33 + 34 - 35 + 36-...- 323 + 324 - 325
3C - C = -325 - 3
2C = -325 - 3
2C = - ( 325 + 3) = - [(34)6. 3 + 3] = - [\(\overline{...1}\)6.3+3] = -[ \(\overline{..3}\) + 3]
2C = - \(\overline{..6}\)
⇒ \(\left[{}\begin{matrix}C=\overline{..3}\\C=\overline{..8}\end{matrix}\right.\)
⇒ C không thể chia hết cho 420 ( xem lại đề bài em nhé)
b, (\(x+1\))2022 + (\(\sqrt{y-1}\) )2023 = 0
Vì (\(x+1\))2022 ≥ 0
\(\sqrt{y-1}\) ≥ 0 ⇒ (\(\sqrt{y-1}\))2023 ≥ 0
Vậy (\(x\) + 1)2022 + (\(\sqrt{y-1}\))2023 = 0
⇔ \(\left\{{}\begin{matrix}\left(x+1\right)^{2022}=0\\\sqrt{y-1}=0\end{matrix}\right.\)
⇔\(\left\{{}\begin{matrix}x+1=0\\y-1=0\end{matrix}\right.\)
⇔\(\left\{{}\begin{matrix}x=-1\\y=1\end{matrix}\right.\)
Kết luận: cặp (\(x,y\)) thỏa mãn đề bài là:
(\(x,y\)) = (-1; 1)