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\(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x-1\right)\left(x+1\right)=27\)
\(\Leftrightarrow x^3+27-x\left(x^2-1\right)=27\)
\(\Leftrightarrow x^3-x^3+x=0\)
\(\Leftrightarrow x=0\)
Vậy x = 0
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3x+2 / 5x+7 = 3x-1 / 5x + 1
=> (3X+2)( 5X+1) = ( 3x-1) ( 5x+7)
=> 3x ( 5x+1) + 2( 5x+1) = 3x( 5x+7) - 5x - 7
15x^2 + 3x + 10x + 2 = 15x^2 + 21x - 5x - 7
15x^2+ 3x + 10x - 15x^2 - 21x + 5x = -7-2
13x - 16x = -9
-3x = -9
x = 3
Vậy x=3
Đúng 1000%
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\(\left(3x-1\right)^{10}=\left(3x-1\right)^{20}\)
\(\Rightarrow\left(3x-1\right)^{20}-\left(3x-1\right)^{10}=0\)
\(\Rightarrow\left(3x-1\right)^{10}\left[\left(3x-1\right)^{10}-1\right]=0\)
\(\Rightarrow\left[{}\begin{matrix}\left(3x-1\right)^{10}=0\\\left(3x-1\right)^{10}-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left(3x-1\right)^{10}=0\\\left(3x-1\right)^{10}=1\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}3x-1=0\\\left[{}\begin{matrix}3x-1=1\\3x-1=-1\end{matrix}\right.\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=\dfrac{2}{3}\\x=0\end{matrix}\right.\)
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Đặt P(x)=0
\(\Leftrightarrow x^2-3x-2=0\)
\(\text{Δ}=\left(-3\right)^2-4\cdot1\cdot\left(-2\right)=17>0\)
Do đó; Phương trình có hai nghiệm phân biệt là:
\(\left\{{}\begin{matrix}x_1=\dfrac{3-\sqrt{17}}{2}\\x_2=\dfrac{3+\sqrt{17}}{2}\end{matrix}\right.\)
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\(\left|2x^2-27\right|^{2019}+\left(5y+12\right)^{2018}=0.\)
\(\text{Ta có}\hept{\begin{cases}\left|2x^2-27\right|^{2019}\ge0\\\left(5y+12\right)^{2018}\ge0\end{cases}}\text{Mà}\left|2x^2-27\right|^{2019}+\left(5y+12\right)^{2018}=0\)
\(\Rightarrow\hept{\begin{cases}\left|2x^2-27\right|^{2019}=0\\\left(5y+12\right)^{2018}=0\end{cases}\Rightarrow\orbr{\begin{cases}\left(2x-27\right)^{2019}=0\\\left(5y+12\right)^{2018}=0\end{cases}\Rightarrow\orbr{\begin{cases}2x-27=0\\5y+12=0\end{cases}\Rightarrow\orbr{\begin{cases}2x=27\\5y=-12\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{27}{2}\\y=\frac{-12}{5}\end{cases}}}}}}\)
\(\text{Vậy}\hept{\begin{cases}x=\frac{27}{2}\\y=\frac{-12}{5}\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) `3x+5 =0`
`3x=-5`
`x=-5/3`
`b) -4x+8=0`
`-4x =-8`
`x=2`
`c) 3x -6=0`
`3x=6`
`x=2`
`d)x^2 +x =0`
`x(x+1) =0`
`=>[(x=0),(x=-1):}`
`e) x^2 -4 =0`
`x^2 =4`
`=> x = +-2`
`f) x^3 -27 =0`
`x^3 =27`
`=> x=3`
`g) 3x^2 +4 =0`
`3x^2 =-4`
`x^2 =-4/3(vô-lí)`
=> Đa thức ko có nghiệm
h) `x^3 -4x =0`
`x(x^2 -4) =0`
`=>[(x=0),(x^2=4 => x=+-2):}`
i) `2x^3 -32x =0`
`2x(x^2 -16)=0`
`=>[(2x=0),(x^2=16):}`
`=>[(x=0),(x=+-4):}`
![](https://rs.olm.vn/images/avt/0.png?1311)
`x^4+3x^2-2=0`
Đặt `x^2=t(t>=0)`
`pt<=>t^2+3t-2=0`
`<=>t^2+3t+9/4=17/4`
`<=>(t+3/2)^2=17/4`
`<=>t+3/2=sqrt{17}/2(do \ t>=0=>t+3/2>=3/2)`
`<=>t=(sqrt{17}-3)/2`
`<=>x^2=(sqrt{17}-3)/2`
`<=>x=+-sqrt{(sqrt{17}-3)/2}`
nguyen ngoc anh:
\(\frac{3x}{27}=27\)
\(\Rightarrow3x:27=27\)
\(\Rightarrow3x=27\times27\)
\(\Rightarrow3x=729\)
\(x=729:3\)
\(x=243\)
Vậy\(x=27\)
Tham khảo nha!
\(\frac{3x}{27}=27\)<=> 3x=729<=> x=243