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\(b,x^2+3x-2=0\\ \Delta=3^2-4.1.\left(-2\right)=17\\ =>\left[{}\begin{matrix}x_1=\dfrac{-3+\sqrt{17}}{2}\\x_2=\dfrac{-3-\sqrt{17}}{2}\end{matrix}\right.\)
Mấy câu còn lại mình giải rồi
x4−3x3−2x2+6x+4=0x4−3x3−2x2+6x+4=0
⇔x4−2x3−2x2−x3+2x2+2x−2x2+4x+4=0⇔x4−2x3−2x2−x3+2x2+2x−2x2+4x+4=0
⇔x2(x2−2x−2)−x(x2−2x−2)−2(x2−2x−2)=0⇔x2(x2−2x−2)−x(x2−2x−2)−2(x2−2x−2)=0
⇔(x2−x−2)(x2−2x−2)=0⇔(x2−x−2)(x2−2x−2)=0
⇔(x+1)(x−2)(x−1−√3)(x−1+√3)=0⇔(x+1)(x−2)(x−1−3)(x−1+3)=0
⇔⎡⎢ ⎢ ⎢ ⎢⎣x=−1x=2x=1+√3x=1−√3
tl
x4−3x3−2x2+6x+4=0x4−3x3−2x2+6x+4=0
⇔x4−2x3−2x2−x3+2x2+2x−2x2+4x+4=0⇔x4−2x3−2x2−x3+2x2+2x−2x2+4x+4=0
⇔x2(x2−2x−2)−x(x2−2x−2)−2(x2−2x−2)=0⇔x2(x2−2x−2)−x(x2−2x−2)−2(x2−2x−2)=0
⇔(x2−x−2)(x2−2x−2)=0⇔(x2−x−2)(x2−2x−2)=0
⇔(x+1)(x−2)(x−1−√3)(x−1+√3)=0⇔(x+1)(x−2)(x−1−3)(x−1+3)=0
⇔⎡⎢ ⎢ ⎢ ⎢⎣x=−1x=2x=1+√3x=1−√3
^HT^
3x3 - 3x2- 6x = 0
x ( 3x2 - 3x - 6 ) = 0
x [ 3x2 + 3x - 6x - 6 ] = 0
x [ 3x ( x + 1 ) - 6 ( x + 1 ) ] = 0
x ( 3x - 6 ) ( x + 1 ) = 0
<=> x = 0 hoặc 3x - 6 = 0 hoặc x + 1 = 0
1) x = 0
2) 3x - 6 = 0 <=> x = 2
3) x + 1 = 0 <=> x = -1
Vậy taaph nghiệm của phương trình đã cho S={0 : -1 : 2 }
\(3x^3-3x^2-6x=0\)
\(3x^3-6x^2+3x^2-6x=0\)
\(3x^2.\left(x-2\right)+3x\left(x-2\right)=0\)
\(\left(3x^2+3x\right)\left(x-2\right)=0\)
\(3x\left(x+1\right)\left(x-2\right)=0\)
\(\Rightarrow3x=0\) \(\Rightarrow x=0\)hoặc \(\orbr{\begin{cases}x+1=0\\x-2=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=-1\\x=2\end{cases}}\)
a: 5-3x=6x+7
=>-3x-6x=7-5
=>-9x=2
=>\(x=-\dfrac{2}{9}\)
b: \(\dfrac{3x-2}{6}-5=3-\dfrac{2\left(x+7\right)}{4}\)
=>\(\dfrac{3x-2}{6}+\dfrac{x+7}{2}=8\)
=>\(\dfrac{3x-2+3\left(x+7\right)}{6}=8\)
=>3x-2+3x+14=48
=>6x+12=48
=>6x=36
=>\(x=\dfrac{36}{6}=6\)
c: \(\left(x-1\right)\left(5x+3\right)=\left(3x-8\right)\left(x-1\right)\)
=>\(\left(x-1\right)\left(5x+3\right)-\left(3x-8\right)\left(x-1\right)=0\)
=>(x-1)(5x+3-3x+8)=0
=>(x-1)(2x+11)=0
=>\(\left[{}\begin{matrix}x-1=0\\2x+11=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{11}{2}\end{matrix}\right.\)
d: \(\left(2x-1\right)^2-\left(x+3\right)^2=0\)
=>\(\left(2x-1-x-3\right)\left(2x-1+x+3\right)=0\)
=>\(\left(x-4\right)\left(3x+2\right)=0\)
=>\(\left[{}\begin{matrix}x-4=0\\3x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-\dfrac{2}{3}\end{matrix}\right.\)
a) \(3x^2-6x=0\)
\(\Rightarrow x=\dfrac{-\left(-6\right)\pm\sqrt{\left(-6\right)^2-4\left(3\cdot0\right)}}{2\cdot3}\)
\(\Rightarrow x=\dfrac{6\pm\sqrt{36}}{6}\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{6+6}{6}\\x=\dfrac{6-6}{6}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=0\end{matrix}\right.\)
b) \(x^2-4=0\)
\(\Rightarrow x=\dfrac{-1\pm\sqrt{\left(-1\right)^2-4\left(1\cdot0\right)}}{2\cdot1}\)
\(\Rightarrow x=\dfrac{-1\pm\sqrt{1}}{2}\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{-1+1}{2}\\x=\dfrac{-1-1}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)
c) \(x^2+6x-7=0\)
\(x=\dfrac{-6\pm\sqrt{\left(-6\right)^2-4\cdot1\cdot\left(-7\right)}}{2\cdot1}\)
\(x=\dfrac{-6\pm\sqrt{36-\left(-28\right)}}{2}\)
\(x=\dfrac{-6\pm8}{2}\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{-6+8}{2}\\x=\dfrac{-6-8}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-7\end{matrix}\right.\)
2)
a) \(\left\{{}\begin{matrix}x-y=1\\x+y=3\end{matrix}\right.\Leftrightarrow2x=\left(x+y\right)+\left(x-y\right)=3+1=4\)
\(\Rightarrow\left\{{}\begin{matrix}x=4:2\\y=\left(x+y\right)-x\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\y=1\end{matrix}\right.\)