Tìm x biết 5( x+4 ) -3 (x-25 ) =x
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\(a.\dfrac{12+x}{42}=\dfrac{35}{42}\Leftrightarrow12+x=35\Leftrightarrow x=23\)
\(b.\dfrac{25-x}{40}=\dfrac{3}{8}\Leftrightarrow\dfrac{25-x}{40}=\dfrac{15}{40}\Leftrightarrow25-x=15\Leftrightarrow x=10\)
\(c.\dfrac{13+x}{20}=\dfrac{3}{4}\Leftrightarrow\dfrac{13+x}{20}=\dfrac{15}{20}\Leftrightarrow13+x=15\Leftrightarrow x=2\)
\(d.\dfrac{23-x}{25}=\dfrac{20}{25}\Leftrightarrow23-x=20\Leftrightarrow x=3\)
x(x+4)(4-x)+(x-5)(x2+5x+25)=3
(x2+4x)(4-x)+x3+5x2+25x-5x2-25x-125=3
4x2-x3+16x-4x2+x3+5x2+25x-5x2-25x=3+125
(4x2-4x2)-(x3-x3)+(16x+25x-25x)+(5x2-5x2)=128
16x=128
x=128:16
x=8
1: =>x=8-35=-27
2: =>15-4+x=6
=>x+11=6
hay x=-5
3: =>-30+25-x=-1
=>x+5=1
hay x=-4
4: =>x-(-13)=-8
=>x+13=-8
hay x=-21
5: =>x-29-17+38=-9
=>x-8=-9
hay x=-1
/x+2/=0\(\Rightarrow x+2=0\Rightarrow x=0-2=-2\)
/x-3/=7-(-2)=9\(\Rightarrow x=9+3=12ho\text{ặc}x=-9+3=-6\)
(7-x)-(25+7)=-25\(\Rightarrow\left(7-x\right)-32=-25\Rightarrow7-x=-25+32=7\Rightarrow x=0\)
/x-3/=/5/+/-7/=5+7=12\(\Rightarrow x=15ho\text{ặc}x=-9\)
/x-5/=/-7/=7\(\Rightarrow x=12ho\text{ặc}x=-2\)
4-(7-x)=x-(13-4)\(\Rightarrow x-3=x-9\Rightarrow x-x=-9+3\Rightarrow0=-6\)(vô lí)
Vậy không có x thoả mãn 4-(7-x)=x-(13-4)
|x+2|=0
Vì |0|=0,suy ra x+2=0
x=0-2
x=-2
Vậy x = -2
|x-3|=7-(-2)
|x-3|=7+2
|x-3|=9
Vì |9|=|-9|=9,suy ra x-3 thuộc{9;-9}
*x-3=9
x =9+3
x =12
*x-3=-9
x=-9+3
x=-6
Vậy x thuộc {12;-6}
`a) x(x + 5)(x – 5) – (x + 2)(x^2 – 2x + 4) = 3`
`<=>x(x^2-25)-(x^3-8)=3`
`<=>x^3-25x-x^3+8=3`
`<=>-25x=-5`
`<=>x=1/5`
`b) (x – 3)^3 – (x – 3)(x^2 + 3x + 9) + 9(x + 1)^2 = 15`
`<=>x^3-9x^2+27x-27-(x^3-27)+9(x^2+2x+1)=15`
`<=>-9x^2+27x+9x^2+18x+9=15`
`<=>45x+9=15`
`<=>45x=6`
`<=>x=6/45=2/15`
`c) (x+5)(x^2 –5x +25) – (x – 7) = x^3`
`<=>x^3-125-x+7=x^3`
`<=>x^3-x-118=x^3`
`<=>-x-118=0`
`<=>-x=118<=>x=-118`
`d) (x+2)(x^2 – 2x + 4) – x(x^2 + 2) = 4 `
`<=>x^3+8-x^3-2x=4`
`<=>8-2x=4`
`<=>2x=4<=>x=2`
Tìm xx biết: \left(x^{4}\right)^{3}=\dfrac{x^{19}}{x^{6}}(x4)3=x6x19
Trả lời: x=x=
5 (x + 4) - 3 (x - 25) = x
5x + 20 - 3x + 75 = x
(5x - 3x) + (20 + 75) = x
2x + 95 = x
2x - x = - 95 (chuyển vế)
=> x = -95