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1) 3x = 45 + 15 = 60
x = 60 : 3 = 20
2) 5x = 50 - 35 = 15
x = 15 : 5 = 3
3) (2x - 5) + 17 = 6
2x - 5 = 6 - 17
2x - 5 = -11
2x = -11 + 5
2x = -6
x = -6 : 2 = -3
4) 10 - 2(4 -3x) = -4
2(4 - 3x) = -4 - 10 = -14
4 - 3x = -14 : 2 = -7
3x = -7 - 4 = -18
x = -18 : 3 = -6
\(\left\{{}\begin{matrix}\left\{{}\begin{matrix}3x-15=45\Leftrightarrow3x=60\Leftrightarrow x=20\\35-5x=50\Leftrightarrow5x=-15\Leftrightarrow x=-3\end{matrix}\right.\\\left\{{}\begin{matrix}\left(2x-5\right)+17=6\Leftrightarrow2x+5=-11\Leftrightarrow2x=-16\Leftrightarrow x=-8\\10-2\left(4-3x\right)=-4\Leftrightarrow8-6x=14\Leftrightarrow6x=-6\Leftrightarrow x=-1\end{matrix}\right.\\\left\{{}\begin{matrix}-12+3\left(-x+7\right)=-18\Leftrightarrow-3x+21=-6\Leftrightarrow-3x=-27\Leftrightarrow x=9\\24:\left(3x-2\right)=-3\Leftrightarrow3x-2=-8\Leftrightarrow3x=-6\Leftrightarrow x=-2\end{matrix}\right.\\-45:5\left(-3-2x\right)=3\Leftrightarrow-15-10x=-15\Leftrightarrow10x=0\Leftrightarrow x=0\end{matrix}\right.\)
a, \(\frac{x}{5}=\frac{-12}{20}\)
\(x=\frac{5.\left(-20\right)}{20}\)
\(x=-5\)
b, 3x - 35 = -45 - 2x
3x + 2x = -45 + 35
5x = -10
x = (-10) : 5
x = -2
c, \(\frac{-1}{6}-x=\frac{5}{12}+\frac{-2}{3}\)
\(\frac{-1}{6}-x=\frac{-1}{4}\)
\(-x=\frac{-1}{6}-\frac{-1}{4}\)
\(-x=\frac{1}{12}\)
\(x=\frac{-1}{12}\)
(x+3).(2x-18)=0
=>x+3=0 hoặc 2x-18 =0
+)x+3=0
x=-3
+)2x-18=0
2x =18
x =9
Vậy x \(\in\)\(_{\left\{-3;9\right\}}\)
\(a.2x+35=x-27\)
\(\Leftrightarrow2x-x=-27-35\)
\(\Rightarrow x=-62\). Vậy \(x=-62\)
\(b.2x-41=3x+\left(-23\right)\)
\(\Leftrightarrow2x-3x=-23+41\)
\(\Leftrightarrow-x=18\)
\(\Rightarrow x=-18\). Vậy \(x=-18\)
\(c.4\left(x-3\right)-3\left(x+5\right)=45.\left(-2\right)-34\)
\(\Leftrightarrow4x-12-3x-15=-124\)
\(\Leftrightarrow4x-3x=-124+12+15\)
\(\Rightarrow x=-97\). Vậy \(x=-97\)
\(d.\left(x+3\right)\left(2x-18\right)=0\)
\(\Leftrightarrow\hept{\begin{cases}x+3=0\\2x-18=0\end{cases}\Rightarrow\hept{\begin{cases}x=-3\\x=9\end{cases}}}\). Vậy \(x=-3;9\)
1,15-(x-7)=-21
x-7=15-(-21)
x-7= 36
x =36+7
x = 43
2,3x+17=2
3x =2-17
3x = -15
x = -15:3
x = -5
3,45-(x-9)=-35
x-9=45-(-35)
x-9=80
x=80+9
x=89
4,(-5)+x=15
x=15-(-5)
x=20
5,2x-(-17)=15
2x+17=15
2x=15-17
2x=-2
x=-2:2
x=-1
3/-7=13
o l m . v n
Toán lớp 6
Lê Hà Vy 24 tháng 4 2016 lúc 18:05
Báo cáo sai phạm
1,15-(x-7)=-21
x-7=15-(-21)
x-7= 36
x =36+7
x = 43
2,3x+17=2
3x =2-17
3x = -15
x = -15:3
x = -5
3,45-(x-9)=-35
x-9=45-(-35)
x-9=80
x=80+9
x=89
4,(-5)+x=15
x=15-(-5)
x=20
5,2x-(-17)=15
2x+17=15
2x=15-17
2x=-2
x=-2:2
x=-1
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3x=64+35
3x=99
x=99:3
x=33
70-5x+15=45
-5x=45-70-15
-5x=-40
x=(-40):(-5)
x=8
70-5(x-3)=45
5(x-3)=70-45
5(x-3)=25
x-3=25:5
x-3=5
x =5+3
x =8