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6 tháng 7 2016

a)      43+(9-21)=317-(x+317)

     ->43+(-12)=317-(x+317)

    ->    31      =317-(x+317) 

     ->  317-(x+317)=31

     ->          x+317 =317-31=286

      ->        x          = 286 - 317

      ->        x          =  -31

Ung ho minh nha

6 tháng 7 2016

a)có người làm rồi

b)(15-x)+(x-12)=7-(-5+x)

=>15-x+x-12=7-(-5)-x

=>(-x+x)+15-12=12-x

=>3=12-x

=>-9=-x

=>x=9

c)đề sai x0 là sao

d)|x|+|y|=1

  • \(\hept{\begin{cases}-1< y\le0\\y=-1-x\end{cases}\Rightarrow}\hept{\begin{cases}0\le y< 1\\y=x-1\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x=\pm1\\y=0\end{cases}}\).Vì x đạt GTTĐ

  • \(\hept{\begin{cases}-1< x\le0\\y=x+1\end{cases}}\Rightarrow\hept{\begin{cases}0\le x< 1\\y=1-x\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x=0\\y=\pm1\end{cases}}\).Vì y đạt GTTĐ

e)(x+1) +(x+3)+(x+5)+...+(x+99)=0

=>(x+x+...+x)+(1+3+...+99)=0

=>50x+2500=0

=>50x=-2500

=>x=-50

6 tháng 7 2016

a 43+(9-21)=317-(x-317)

43+(-10)=317-x-317

31=(317-317)-x

31=-x

x=-31

h minh nha

5 tháng 2 2020

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

28 tháng 2 2020

a , 43 + ( 9 - 21 ) = 317 - ( x + 317 )

b , ( 15 - x ) + ( x - 12 ) = 7 - ( -5 + x )

c , x - { 57 - [ 42 + ( -23 - x )]} = 13 - { 47 + [ 25 - ( 32 - x )]}

d , -7 + | x - 4 | = -3

4 tháng 2 2020

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 \(x\in\left\{-1;-3;0;-4;1;-5;2;-6\right\}\)

5 tháng 2 2020

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}

7 tháng 7 2018

a,x+(-45)=(-62)+17

<=>x=(-62)+17+45

<=>x=0

b,x+29=\(|-43|\)-+(-43)

<=>x=43-43-29

<=>x=-29

c,43+(9-21)=317-(x+317)

<=>31=317-x-317

<=>31=-x

<=>-31=x

d, (15-x)+(x-12)=7-(-5-x)

<=>15-x+x-12=7+5+x

<=>3=12+x

<=>-9=x

e, x-{57-[42+(-23-x)]}=13-{47+[25-(32-x)]}

<=>x-57+42-23-x=13-47-25+32-x

<=>76=-27-x

<=>103=-x

<=>-103=x

f,\(|x|+|-4|=7\)

<=>\(|x|\)+4=7

<=>\(|x|\)=3

<=>x=3 hoặc x=-3

28 tháng 2 2020

a.  x + (-45) = (-62 ) + 17

b.  x + 29 = /-43/ + (-43)

c.  43 + (9 - 21) = 317 - ( x +317)

d.  (15 - x ) + ( x - 12 ) = 7 - ( -5 + x )

e.  x - { 57 - [ 42 + ( -23 - x ) ] } = 13 - { 47 + [ 25 - ( 32 - x ) ] }

13 tháng 1 2018

1.a)43+(9-21)=317-(x+317)

<=>31=317-317-x

<=>x=-31

b)(15-x)+(x-12)=7-(-5+x)

<=>15-12-x+x=7+5-x

<=>x=12-3=9

c)-{57-[42+(-23-x)]}=13-{47+[25-(32-x)]}

<=>-{57-[42-23-x]}=13-{47+[25-31+x]}

<=>-{57-19+x}=13-{47-6+x}

<=>-38-x=-28-x

<=>0x=10

<=>x\(\in\varnothing\)

13 tháng 1 2018

dau /../ là sao bạn

7 tháng 7 2017

bài 2:

a. Ta có : (a-b)-(b+c)+(c-a)-(a-b-c)

= a-b-b-c+c-a-a+b+c

=-a-b+c=-(a+b-c)

a: \(\left(15-x\right)+\left(x-12\right)=7-\left(x-5\right)\)

=>7-x+5=15-x+x-12

=>12-x=3

hay x=9

b: \(\Leftrightarrow x-\left\{57-\left[42-23-x\right]\right\}=13-\left\{47+25-32+x\right\}\)

\(\Leftrightarrow x-\left\{57-19+x\right\}=13-\left\{40+x\right\}\)

=>x-38-x=13-40-x

=>-27-x=-38

=>x+27=38

hay x=11

e: \(x^2+3x+9⋮x+3\)

\(\Leftrightarrow x\left(x+3\right)+9⋮x+3\)

\(\Leftrightarrow x+3\in\left\{1;-1;9;-9;3;-3\right\}\)

hay \(x\in\left\{-2;-4;6;-12;0;-6\right\}\)

 

30 tháng 12 2019

\(43+\left(9-21\right)=317\left(x+317\right)\)

\(\Rightarrow317-\left(x+317\right)=43+\left(9-21\right)\)

\(\Rightarrow317-\left(x+317\right)=43+\left(-12\right)\)

\(\Rightarrow317-\left(x+317\right)=31\)

\(\Rightarrow x+317=317-31\)

\(\Rightarrow x+317=286\)

\(\Rightarrow x=286-317\)

\(\Rightarrow x=-31\)

Vay x = -31

\(b.\left(15-x\right)+\left(x-12\right)=7-\left(-5+x\right)\)

\(\Rightarrow15-x+x-12=7+5+x\)

\(\Rightarrow15-12=12-x\)

\(\Rightarrow3=12-x\)

\(\Rightarrow12-x=3\)

\(\Rightarrow x=12-3\)

\(\Rightarrow x=9\)

Vay x = 9 

....

30 tháng 12 2019

a) 43+(9-21) = 317-(x+317)

43+(-12) = 317-(x+317)

317-(x+317) = 31

x+317 = 317-31=286

x = 286-317=(-31)

Tạm thời câu b mình chưa nghĩ ra nha.