help meeeee
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a) \(\left(3x-1\right)^6=\left(3x-1\right)^4\)
\(\Rightarrow\left[{}\begin{matrix}3x-1=0\\3x-1=1\\3x-1=-1\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=\dfrac{2}{3}\\x=0\end{matrix}\right.\)
b) Áp dụng t/c dtsbn:
\(\dfrac{a+b-c}{c}=\dfrac{a-b+c}{b}=\dfrac{-a+b+c}{a}=\dfrac{a+b+c}{a+b+c}=1\)
\(\Rightarrow\left\{{}\begin{matrix}a+b-c=c\\a-b+c=b\\-a+b+c=a\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}a+b=2c\\a+c=2b\\b+c=2a\end{matrix}\right.\)
\(\Rightarrow M=\dfrac{\left(a+b\right)\left(b+c\right)\left(c+a\right)}{abc}=\dfrac{2a.2b.2c}{abc}=8\)
1 went
2 have never been
3 haven't seen
4 saw
5 have they been
6 got
7 have already done
1. I went to the new Mexican restaurant yesterday.
2. I have never been there. Did you like it?
3. I have not seen Ann for a very long time.
4. Really? I saw her yesterday at the gym.
5. How long have they been married?
6. Only a year. They got married last June.
7. No, you don't have to. I have already done it.
Ta có :
\(\dfrac{x}{5}=\dfrac{2}{3}\)
\(\Rightarrow x.3=5.2\)
\(x.3=10\)
\(x=10:3\)
\(x=\dfrac{10}{3}\)
Vậy \(x=\dfrac{10}{3}\) là giá trị cần tìm
Ta có :\(\dfrac{x}{5}=\dfrac{2}{3}\)
\(\Rightarrow x.3=2.5\)
\(x.3=10\)
\(x=10:3\)
\(\Rightarrow x=\dfrac{10}{3}\)
Vậy \(x=\dfrac{10}{3}\)
Vậy \(x=\dfrac{10}{3}\)
\(=\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{2008}{2009}\)
\(=\dfrac{1}{2009}\)
=> B
B