tìm x biết \(x^2-4x+8=5\)
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Ta thấy \(\left|x+\frac{1}{8}\right|\ge0\forall x;\left|x+\frac{2}{8}\right|\ge0\forall x;\left|x+\frac{5}{8}\right|\ge0\forall x\)
\(\Rightarrow\left|x+\frac{1}{8}\right|+\left|x+\frac{2}{8}\right|+\left|x+\frac{5}{8}\right|\ge0\)
\(\Rightarrow4x\ge0\Rightarrow x\ge0\)
\(\Rightarrow x+\frac{1}{8}+x+\frac{2}{8}+x+\frac{5}{8}=4x\)
\(\Rightarrow3x+1=4x\)
=> x = 1 (t/m)
Vậy x=1
a) $(x-3)^2-(x+2)(x-2)=-5$
$\Rightarrow x^2-2\cdot x\cdot3+3^2-(x^2-2^2)=-5$
$\Rightarrow x^2-6x+9-(x^2-4)=-5$
$\Rightarrow x^2-6x+9-x^2+4=-5$
$\Rightarrow-6x+13=-5$
$\Rightarrow-6x=-18$
$\Rightarrow x=3$
b) $x^3-2x^2-4x+8=0$
$\Rightarrow(x^3-2x^2)-(4x-8)=0$
$\Rightarrow x^2(x-2)-4(x-2)=0$
$\Rightarrow (x^2-4)(x-2)=0$
$\Rightarrow (x^2-2^2)(x-2)=0$
$\Rightarrow (x-2)(x+2)(x-2)=0$
$\Rightarrow (x-2)^2(x+2)=0$
\(\Rightarrow\left[{}\begin{matrix}x-2=0\\x+2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\)
$\text{#}Toru$
a, x^2-4=8(x-2)
=> x^2 - 4 = 8.x - 16
=> x^2 = (8.x - 16) - 4
=> x^2 = 8.x - (16+4)
=> x^2 = 8.x - 20
A, \(x^2-4=8\left(x-2\right)\)=> \(\left(x-2\right).\left(x+2\right)=8\left(x-2\right)=>\left(x-2\right).\left(x+2\right)-8\left(x-2\right)=0\)
=>\(\left(x-2\right).\left(x-6\right)=0\)
=> x = 2 hoặc x =6
B. \(x^2-4x+4=9\left(x-2\right)\)=> \(\left(x-2\right)^2=9\left(x-2\right)=>\left(x-2\right)^2-9\left(x-2\right)=0\)
=>\(\left(x-2\right).\left(x-11\right)=0\)=> x =2 hoặc x =11
C. \(4x^2-12x+9=\left(5-x\right)^2=>\left(2x-3\right)^2=\left(5-x\right)^2\)
=>\(\left(2x-3\right)^2-\left(5-x\right)^2=>\left(3x-8\right).\left(x+2\right)=0\)
=> x = 3/8 hoặc x = - 2
Tìm x biết
1. 2(5x-8)-3(4x-5)=4(3x-4)+11
2. (2x+1)2-(4x-1).(x-3)-15=0
3. (3x-1).(2x-7)-(1-3x).(6x-5)=0
1) \(\Rightarrow10x-16-12x+15=12x-16+11\)
\(\Rightarrow14x=4\Rightarrow x=\dfrac{2}{7}\)
2) \(\Rightarrow4x^2+4x+1-4x^2+13x-3-15=0\)
\(\Rightarrow17x=17\Rightarrow x=1\)
3) \(\Rightarrow\left(3x-1\right)\left(2x-7+6x-5\right)=0\)
\(\Rightarrow\left(2x-3\right)\left(3x-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=\dfrac{1}{3}\end{matrix}\right.\)
2: Ta có: \(\left(2x+1\right)^2-\left(4x-1\right)\left(x-3\right)-15=0\)
\(\Leftrightarrow4x^2+4x+1-4x^2+12x+x-3-15=0\)
\(\Leftrightarrow17x=17\)
hay x=1
\(a,\Leftrightarrow\dfrac{3x^3+6x^2-3x-5x^2-10x+5}{x^2+2x-1}=10\\ \Leftrightarrow\dfrac{3x\left(x^2+2x-1\right)-5\left(x^2+2x-1\right)}{x^2+2x-1}=10\\ \Leftrightarrow3x-5=10\Leftrightarrow3x=15\Leftrightarrow x=5\\ b,\Leftrightarrow\left(x^4+2x^2-4x^2-8\right):\left(x-2\right)=0\\ \Leftrightarrow\left[\left(x^2-4\right)\left(x^2+2\right)\right]:\left(x-2\right)=0\\ \Leftrightarrow\left[\left(x-2\right)\left(x+2\right)\left(x^2+2\right)\right]:\left(x-2\right)=0\\ \Leftrightarrow\left(x+2\right)\left(x^2+2\right)=0\Leftrightarrow x=-2\left(x^2+2>0\right)\\ c,\Leftrightarrow\dfrac{x\left(x-4\right)}{\left(x-4\right)^2}=0\Leftrightarrow\dfrac{x}{x-4}=0\Leftrightarrow x=0\)
b: \(\Leftrightarrow x^4-4x^2+2x^2-8=0\)
hay x=-2
<=> x2 - 4x + 3 = 0
<=> x2 - x - 3x + 3 = 0
<=> x(x - 1) - 3(x - 1) = 0
<=> (x - 3)(x - 1) = 0 <=> \(\orbr{\begin{cases}x=3\\x=1\end{cases}}\)
Vậy ...
x2 - x - 3x + 3 = 0
x( x - 1) - 3( x - 1) = 0
(x - 3) ( x - 1) = 0
TH 1: x-3=0
x=3
TH2: x-1=0
x=1