Tìm X biết:
a. 90 : X = 6
b. X : 5 = 83
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`x :3*5 = 3/4 :(-5/6)`
`x :15 =3/4*(-6/5)=-9/10`
`x = -9/10 *15 =-27/2`
`x-1*2/2 = 8/x -1.2`
`x- 1*1 = 8/x -2`
`x-8/x = -2+1`
`x-8/x =-1`
`x^2 -8x =-x`
`x^2 -8x +x=0`
`x^2 -7x =0`
`x(x-7) =0`
`=>[(x=0),(x=7):}`
`a, x \div 15=-9/10`
`x=-9/10*14`
`x=-27/2`
`b, (x-1*2)/2=8/(x-1*2)`
\(\left(x-1\cdot2\right)\cdot\left(x-1\cdot2\right)=8\cdot2\)
`(x-1*2)^2=16`
`(x-1*2)^2=(+-4)^2`
\(\Rightarrow\left[{}\begin{matrix}x-1\cdot2=4\\x-1\cdot2=-4\end{matrix}\right.\)
`=>`\(\left[{}\begin{matrix}x-2=4\\x-2=-4\end{matrix}\right.\)
`=>`\(\left[{}\begin{matrix}x=4+2\\x=\left(-4\right)+2\end{matrix}\right.\)
`=>`\(\left[{}\begin{matrix}x=6\\x=-2\end{matrix}\right.\)
\(x\left(5-6x\right)+\left(2x-1\right)\left(3x+\text{4}\right)=6\\ \Leftrightarrow5x-6x^2+6x^2+8x-3x-4=6\)
\(\Leftrightarrow10x-4=6\)
\(\Leftrightarrow10x=6+4\\ \Leftrightarrow10x=10\\ \Leftrightarrow x=\dfrac{10}{10}\)
\(\Leftrightarrow x=1\)
\(x^2\left(x-2021\right)-x+2021=0\)
\(\Leftrightarrow x^2\left(x-2021\right)-(x-2021)=0\)
\(\Leftrightarrow\left(x-2021\right)\left(x^2-1\right)=0\)
\(\Leftrightarrow\left(x-2021\right)\left(x-1\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-2021=0\\x-1=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2021\\x=1\\x=-1\end{matrix}\right.\)
\(a,\Rightarrow5x+3x^2-3x^2-x+2=6\\ \Rightarrow4x=4\Rightarrow x=1\\ b,\Rightarrow\left(2x+\dfrac{1}{2}-1+2x\right)\left(2x+\dfrac{1}{2}+1-2x\right)=2\\ \Rightarrow\dfrac{3}{2}\left(4x-\dfrac{1}{2}\right)=2\\ \Rightarrow6x-\dfrac{3}{4}=2\\ \Rightarrow6x=\dfrac{11}{4}\\ \Rightarrow x=\dfrac{11}{24}\\ c,\Rightarrow\left(x+3\right)\left(x-2\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\)
`a) 3-5+(-x+3)=6`
`=>5+(-x+3)=3-6`
`=>5+(-x+3)=-3`
`=>-x+3=-3-5`
`=>-x+3=-8`
`=>-x=-8-3`
`=>-x=-11`
`=>x=11`
__
`b)(-4-x)+(4-15)=-15`
`=>(-4-x)+-11=-15`
`=>-4-x=-15-(-11)`
`=>-4-x=-15+11`
`=>-4-x=-4`
`=>x=-4-(-4)`
`=>x=-4+4`
`=>x=0`
`c)(11+x)-(-11-9)=32`
`=>(11+x)-(-20)=32`
`=>(11+x)+20=32`
`=>11+x=32-20`
`=>11+x=12`
`=>x=12-11`
`=>x=1`
`a)3-5+(-x+3)=6`
`5+(-x+3)=3-6`
`5+(-x+3)=-3`
`-x+3=-3-5`
`-x+3=-8`
`-x=-8-3`
`-x=-11`
`x=11`
`b,(-4-x)+(4-15)=-15`
`(-4-x)+(-11)=-15`
`-4-x=-15-(-11)`
`-4-x=-15+11`
`-4-x=-4`
`x=-4-(-4)`
`x=-4+4`
`x=0`
`c)(11+x)-(-11-9)=32`
`(11+x)-(-20)=32`
`(11+x)+20=32`
`11+x=32-20`
`11+x=12`
`x=12-11`
`x=1`
\(a,\left(2x-5\right)+17=6\\ \Rightarrow2x-5=-11\\ \Rightarrow2x=-6\\ \Rightarrow x=-3\\ b,10-2\left(4-3x\right)=-4\\ \Rightarrow2\left(4-3x\right)=14\\ \Rightarrow4-3x=7\\ \Rightarrow3x=-3\\ \Rightarrow x=-1\\ c,24:\left(3x-2\right)=-3\\ \Rightarrow3x-2=-8\\ \Rightarrow3x=-6\\ \Rightarrow x=-2\\ d,5-2x=-17+12\\ \Rightarrow5-2x=-5\\ \Rightarrow2x=10\\ \Rightarrow x=5\)
a: =>2x-5=-11
=>2x=-6
hay x=-3
b: =>2(4-3x)=14
=>4-3x=7
=>3x=-3
hay x=-1
c: =>3x-2=-8
=>3x=-6
hay x=-2
`a)5x(x-1)-(x+2)(5x-7)=6`
`<=>5x^2-5x-(5x^2-7x+10x-14)=6`
`<=>5x^2-5x-(5x^2+3x-14)=6`
`<=>-8x+14=6`
`<=>8x=8<=>x=1`
Vậy `x=1`
`b)(x+2)^2-(x^2-4)=0`
`<=>x^2+4x+4-x^2+4=0`
`<=>4x+8=0`
`<=>4x=-8`
`<=>x=-2`
Vậy `x=-2`
\(a,\Leftrightarrow x^2-2x-x^2+5x=6\\ \Leftrightarrow3x=6\\ \Leftrightarrow x=2\)
\(b,\Leftrightarrow x^2-6x+9-x+9=0\\ \Leftrightarrow x^2-7x+18=0\\ \Leftrightarrow\left(x^2-7x+\dfrac{49}{4}\right)+\dfrac{23}{4}=0\\ \Leftrightarrow\left(x-\dfrac{7}{2}\right)^2+\dfrac{23}{4}=0\left(vôlí\right)\)
a)Vì 84⋮x➩ x∈ƯC(84;180)
180⋮x
Ta có:
24=23.3
180=22.32.5
ƯCLN(...)=22.3=12
ƯC(...)=Ư(12)={1;2;3;4;6;12}
Vì 84⋮x;180⋮x và x≥6
⇔x={6;12}
b)x⋮28;x⋮56;x⋮70➩x∈BC(...)
Ta có:28=22.7
56=23.7
70=2.5.7
BCNN(...)=23.5.7=280
BC(...)=B(280)={0;280;560;840;...}
Vì x⋮28;x⋮56;x⋮70 và 500<x<600
⇔x=280
c)x⋮12➩x=B(12)
B(12)={0;12;24;36;48;60;72;...}
Vì x⋮12 và x<60
⇔ x={0;12;24;48}
a. 90 : X = 6
X = 15
b. X : 5 = 83
X = 415