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a) x - 7 = 5. 0 => x - 7 = 0 =>x = 7.
b) x: 3 = 47 +13 => x: 3 = 60 => x = 60.3 => x = 180.
c) x : 7 - 7 = 0 hoặc x : 12 - 12 = 0. Do đó x = 49 hoặc x = 144.
d) x : 2 = 150 - 135 => x: 2 = 15 => x = 15.2 => x = 30.
e) 100: x = 140 -120 => 100: x = 20 => x = 100:20 => x = 5.
g) x : 5 = 300 - 273 => x : 5 = 27 =>x = 27.5 => x = 135
a) x - 7 = 5. 0 => x - 7 = 0 =>x = 7.
b) x: 3 = 47 +13 => x: 3 = 60 => x = 60.3 => x = 180.
c) x : 7 - 7 = 0 hoặc x : 12 - 12 = 0. Do đó x = 49 hoặc x = 144.
d) x : 2 = 150 - 135 => x: 2 = 15 => x = 15.2 => x = 30.
e) 100: x = 140 -120 => 100: x = 20 => x = 100:20 => x = 5.
g) x : 5 = 300 - 273 => x : 5 = 27 =>x = 27.5 => x = 135
Bài làm :
\(a\text{)}...\Leftrightarrow\orbr{\begin{cases}x\div7-7=0\\x.3-12=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x\div7=7\\x.3=12\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=49\\x=4\end{cases}}\)
\(b\text{)}\Leftrightarrow...\Leftrightarrow x\div2=15\Leftrightarrow x=15.2=30\)
\(c\text{)}...\Leftrightarrow100\div x=20\Leftrightarrow x=100\div20=5\)
\(d\text{)}...\Leftrightarrow x\div5=27\Leftrightarrow x=27.5=135\)
\(a,\left(x-7\right):5=0\)
\(\Rightarrow x-7=0\)
\(\Rightarrow x=7\)
\(b,\left(x:7-7\right)\left(x:12-12\right)=0\)
\(\Rightarrow\hept{\begin{cases}x:7=7\\x:12=12\end{cases}}\)
\(\Rightarrow x=1\)
\(c,300-x:5=273\)
\(\Rightarrow x:5=27\)
\(\Rightarrow x=27.5=135\)
\(d,135+x:2=150\)
\(\Rightarrow x:2=15\)
\(\Rightarrow x=30\)
a) \(\left(x-7\right):5=0\)
\(\Rightarrow x-7=0\times5\)
\(\Rightarrow x-7=0\)
\(\Rightarrow x=0+7\)
\(\Rightarrow x=7\)
Vậy x = 7
b) \(\left(x:7-7\right)\left(x:12-12\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x:7-7=0\\x:12-12=0\end{cases}}\Rightarrow\orbr{\begin{cases}x:7=7\\x:12=12\end{cases}}\Rightarrow\orbr{\begin{cases}x=49\\x=144\end{cases}}\)
Vậy x = 49 hoặc x = 144
c) \(300-x:5=273\)
\(\Rightarrow x:5=300-273\)
\(\Rightarrow x:5=27\)
\(\Rightarrow x=27\times5\)
\(\Rightarrow x=135\)
Vậy x = 135
d) \(135+x:2=150\)
\(\Rightarrow x:2=150-135\)
\(\Rightarrow x:2=15\)
\(\Rightarrow x=15\times2\)
\(\Rightarrow x=30\)
Vậy x = 30
_Chúc bạn học tốt_
b) -26 - ( x - 7 ) = 0
x - 7 = -26 - 0
x - 7 = -26
x = -26 + 7
x = -19
Bài 2 :
a) 3 - ( 17 - x ) = -12
( 17 - x ) = 3 - ( -12 )
( 17 - x ) = 15
x = 17 - 15
x = 2
a, 43 + ( 9 - 21 ) = 317 - ( x + 317 )
43 + ( -12 ) = 317 - x - 317
43 - 12 = 317 - 317 - x
-x = 31
x = -31
b, (15-x) + (x-12) = 7- (-5 + x)
15-x+x-12 = 7+5-x
15-12 = 12-x
3 = 12-x
x = 12-3
x = 9
c, x - { 57- [42+ (-23 - x)]} = 13- {47+ [25- (32-x)]}
x - [57- (42-23-x)] = 13- [47+ (25-32+x)]
x - [57- (19-x)] = 13- [47+ (x-7)]
x - (57-19+x) = 13- (47+x-7)
x - (38+x) = 13- (40+x)
x-38-x = 13-40-x
x = 13-40+38
x = 11
a) \(43+\left(9-21\right)=317-\left(x+317\right)\\ 43+9-21=317-x-317\\ 52-21=\left(317-317\right)-x\\ 31=-x\\ x=-31\)Vậy x = -31
b) \(\left(15-x\right)+\left(x-12\right)=7-\left(-5+x\right)\\ 15-x+x-12=7+5-x\\ \left(x-x\right)+\left(15-12\right)=12-x\\ 3=12-x\\ x=9\)Vậy x = 9
c) \(x-\left\{57-\left[42+\left(-23-x\right)\right]\right\}=13-\left\{47+\left[25-\left(32-x\right)\right]\right\}\\ x-\left\{57-\left[42+\left(-23\right)-x\right]\right\}=13-\left\{47+\left[25-32+x\right]\right\}\\ x-\left\{57-42+23+x\right\}=13-\left\{47+25-32+x\right\}\\ x-57+42-23-x=13-47-25+32-x\\ -57+42-23=-34-25+32-x\\ -15-23=-59+32-x\\ -38=-27-x\\ x=11\)Vậy x = 11
d) \(-7+\left|x-4\right|=-3\\ \left|x-4\right|=4\\ \Rightarrow\left[{}\begin{matrix}x-4=4\\x-4=-4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=8\\x=0\end{matrix}\right.\)Vậy \(x\in\left\{8;0\right\}\)
e) \(13-\left|x+5\right|=13\\ \left|x+5\right|=0\\ \Rightarrow x+5=0\\ \Rightarrow x=-5\)Vậy x = -5
g) \(\left|x-10\right|-\left(-12\right)=4\\ \left|x-10\right|=-8\\ \Rightarrow x\in\varnothing\left(\text{vì }\left|x-10\right|\ge0\text{với mọi }x\right)\)Vậy \(x\in\varnothing\)
h) \(\left|x+2\right|< 5\\ 0\le\left|x+2\right|< 5\\ \Rightarrow\left|x+2\right|\in\left\{1;2;3;4\right\}\\ \Rightarrow x+2\in\left\{1;-1;2;-2;3;-3;4;-4\right\}\\ \Rightarrow x\in\left\{-1;-3;0;-4;1;-5;2;-6\right\}\)Vậy \(x\in\left\{-1;-3;0;-4;1;-5;2;-6\right\}\)
a) 43+(9−21)=317−(x+317)43+9−21=317−x−31752−21=(317−317)−x31=−xx=−3143+(9−21)=317−(x+317)43+9−21=317−x−31752−21=(317−317)−x31=−xx=−31Vậy x = -31
b) (15−x)+(x−12)=7−(−5+x)15−x+x−12=7+5−x(x−x)+(15−12)=12−x3=12−xx=9(15−x)+(x−12)=7−(−5+x)15−x+x−12=7+5−x(x−x)+(15−12)=12−x3=12−xx=9Vậy x = 9
c) x−{57−[42+(−23−x)]}=13−{47+[25−(32−x)]}x−{57−[42+(−23)−x]}=13−{47+[25−32+x]}x−{57−42+23+x}=13−{47+25−32+x}x−57+42−23−x=13−47−25+32−x−57+42−23=−34−25+32−x−15−23=−59+32−x−38=−27−xx=11x−{57−[42+(−23−x)]}=13−{47+[25−(32−x)]}x−{57−[42+(−23)−x]}=13−{47+[25−32+x]}x−{57−42+23+x}=13−{47+25−32+x}x−57+42−23−x=13−47−25+32−x−57+42−23=−34−25+32−x−15−23=−59+32−x−38=−27−xx=11Vậy x = 11
d) −7+|x−4|=−3|x−4|=4⇒[x−4=4x−4=−4⇒[x=8x=0−7+|x−4|=−3|x−4|=4⇒[x−4=4x−4=−4⇒[x=8x=0Vậy x∈{8;0}x∈{8;0}
e) 13−|x+5|=13|x+5|=0⇒x+5=0⇒x=−513−|x+5|=13|x+5|=0⇒x+5=0⇒x=−5Vậy x = -5
g) |x−10|−(−12)=4|x−10|=−8⇒x∈∅(vì |x−10|≥0với mọi x)|x−10|−(−12)=4|x−10|=−8⇒x∈∅(vì |x−10|≥0với mọi x)Vậy x∈∅x∈∅
h) |x+2|<50≤|x+2|<5⇒|x+2|∈{1;2;3;4}⇒x+2∈{1;−1;2;−2;3;−3;4;−4}⇒x∈{−1;−3;0;−4;1;−5;2;−6}|x+2|<50≤|x+2|<5⇒|x+2|∈{1;2;3;4}⇒x+2∈{1;−1;2;−2;3;−3;4;−4}⇒x∈{−1;−3;0;−4;1;−5;2;−6}Vậy x∈{−1;−3;0;−4;1;−5;2;−6}
a, x=5
b,x=20
c,x=1 hoặc x=-2
d, ko hiểu đề bài
e,x=2
f,x=80
\(a)\left(x-5\right).2=0\)
\(\Rightarrow x-5=0\)
\(\Rightarrow x=5\)
Vậy \(x=5\)
\(b)x.3-13=47\)
\(\Rightarrow x.3=47+13\)
\(\Rightarrow x.3=60\)
\(\Rightarrow x=60:3\)
\(\Rightarrow x=20\)
Vậy \(x=20\)
\(c)\left(x.7-7\right)\left(x.12+24\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x.7-7=0\Rightarrow x.7=7\Rightarrow x=1\\x.12+24=0\Rightarrow x.12=-24\Rightarrow x=-2\end{cases}}\)
Vậy\(x\in\left\{1;-2\right\}\)
\(e)140-10.x=120\)
\(\Rightarrow10.x=140-120\)
\(\Rightarrow10.x=20\)
\(\Rightarrow x=2\)
Vậy \(x=2\)
\(g)x.5-127=273\)
\(\Rightarrow x.5=273+127\)
\(\Rightarrow x.5=400\)
\(\Rightarrow x=400:5\)
\(\Rightarrow x=80\)
Vậy \(x=80\)