tìm X và Y biết
( X - 3 )2= ( x - 3 ) 4
( X -2 ) . ( Y- 3 ) = 0
giải rõ
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\(\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+........+\frac{1}{99\cdot100}\right)-2x=\frac{1}{2}\)
\(\left(\frac{2-1}{1\cdot2}+\frac{3-2}{2\cdot3}+\frac{4-3}{3\cdot4}+...+\frac{100-99}{99\cdot100}\right)-2x=\frac{1}{2}\)
\(\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{99}-\frac{1}{100}\right)-2x=\frac{1}{2}\)
\(\left(1-\frac{1}{100}\right)-2x=\frac{1}{2}\)
\(\frac{99}{100}-2x=\frac{1}{2}\)
\(2x=\frac{99}{100}-\frac{1}{2}\)
\(2x=\frac{49}{100}\)
\(x=\frac{49}{100}:2\)
\(x=\frac{49}{200}\)
\(\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)-2x=\frac{1}{2}\)
\(\frac{99}{100}-2x=\frac{1}{2}\)
\(\frac{99-50}{100}=2x\)
\(49=200x\)
\(x=\frac{49}{200}\)
Ta có:
\(y\left(y-1\right)=6\)
\(\Leftrightarrow y^2-y-6=0\)
\(\Leftrightarrow y^2-3y+2y-6=0\)
\(\Leftrightarrow y\left(y-3\right)+2\left(y-3\right)=0\)
\(\Leftrightarrow\left(y-3\right)\left(y+2\right)=0\Leftrightarrow\orbr{\begin{cases}y-3=0\\y+2=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}y=3\\y=-2\end{cases}}\)
\(\left(x-2\right)^4=16\)
\(\left(x-2\right)^4=2^4=\left(-2\right)^4\)
\(=>\orbr{\begin{cases}x-2=2\\x-2=-2\end{cases}}\)
\(=>\orbr{\begin{cases}x=4\\x=0\end{cases}}\)
Vậy ....
b, \(\left(5-x\right)^3=8\)
\(\Rightarrow\) \(\left(5-x\right)^3=2^3\)
\(\Rightarrow\) \(5-x=2\)
\(\Rightarrow\) \(x=3\)
c, \(5^x.125=5^6\)
\(\Rightarrow\) \(5^x.5^3=5^6\)
\(\Rightarrow\) \(5^{x+3}=5^6\)
\(\Rightarrow\) \(x+3=6\)
\(\Rightarrow\) \(x=3\)
\(\left(x-3\right)^2=\left(x-3\right)^4.\)
\(\Rightarrow\left(x-3\right)^4-\left(x-3\right)^2=0\)
\(\Rightarrow\left(x-3\right)^2\left[\left(x-3\right)^2-1\right]=0\)
\(\Rightarrow\orbr{\begin{cases}\left(x-3\right)^2=0\\\left(x-3\right)^2-1=0\end{cases}\Rightarrow\orbr{\begin{cases}x-3=0\\\left(x-3\right)^2=1\end{cases}\Rightarrow\orbr{\begin{cases}x=0+3\\\left(x-3\right)^2=1\end{cases}\Rightarrow}}\hept{\begin{cases}x=3\\x-3=1\\x-3=-1\end{cases}}}\Rightarrow\hept{\begin{cases}x=3\\x=4\\x=2\end{cases}}\)
\(\left(x-2\right)\left(y-3\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-2=0\\y-3=0\end{cases}\Rightarrow\orbr{\begin{cases}x=0+2=2\\y=0+3=3\end{cases}}}\)