TÌM x:
x - 2 =3
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\(x-\dfrac{1}{4}=\dfrac{-21}{10}\)
\(x=\dfrac{-21}{10}+\dfrac{1}{4}\)
\(x=\dfrac{-42}{20}+\dfrac{5}{20}=\dfrac{-37}{20}\)
\(\Leftrightarrow x+\dfrac{1}{8}=\dfrac{1}{6}\\ \Leftrightarrow x=\dfrac{1}{24}\)
\(\Rightarrow x+\dfrac{1}{8}=\dfrac{1}{6}\\ \Rightarrow x=\dfrac{1}{24}\)
\(\Leftrightarrow x^3+2x^2-3x-x^3-3x^2=-4\)
\(\Leftrightarrow x^2+3x-4=0\)
=>(x+4)(x-1)=0
=>x=-4 hoặc x=1
\(x^3-5x^2-9x+45=0\)
=>\(x^2\left(x-5\right)-9\left(x-5\right)=0\)
=>\(\left(x-5\right)\left(x^2-9\right)=0\)
=>\(\left(x-5\right)\left(x-3\right)\left(x+3\right)=0\)
=>\(\left[{}\begin{matrix}x-5=0\\x-3=0\\x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=3\\x=-3\end{matrix}\right.\)
`x^3 -5x^2 -9x+45=0`
`<=> (x^3 -5x^2 )-(9x-45)=0`
`<=> x^2 (x-5)- 9(x-5)=0`
`<=>(x-5)(x^2 -9)=0`
`<=>(x-5)(x-3)(x+3)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x-5=0\\x-3=0\\x+3=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=5\\x=3\\x=-3\end{matrix}\right.\)
\(\Leftrightarrow\left(x+2\right)^2\cdot\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=-1\end{matrix}\right.\)
x-2=3
x=3+2
x=5
x-2=3
x =3+2
x =5