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ta có
a)[ (-2)+7] +[(-12)+17]+....+[(-52)+57]
= 5+5+5+...+5 có 6 số 5
=5x6
=30
b)(-30)+(-29)+....48+49+50
=[(-30)+30] +....+31+32+...+50
=0+..+0+31+32+....+50
=0+31+32+..+50
=810
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
a,(-2)+7+(-12)+17+...+(-52)+57
=[(-2)+7]+[(-12)+17]+...+[(-52)+57]
=5+5+5+...+5 có 6 số 5
=5.6
=30
b,(-30)+(-29)+...+48+49+50
=[(-30)+(-29)]+...+31+32+...+50
=0+0+...+31+32+...+50
=0+31+32+...+50
=810
x+(-7)=-20
x=-20+7
x=-13
x=-15=5 (lỗi đề sao x vừa bằng -15 vừa bằng 5 đc)
-95+x=10
x=10+95
x=105
8+x=-12
x=-12-8
x=-20
x+(-45)=-62+17
x-45=-45
x=-45+45
x=0
x+29=|-43|+43
x+29=0
x=0-29
x=-29
43+(9-21)=317-(x+317)
31=0-x
x=0-31
x=-31
|x|+|-4|=7
|x|=7-4
|x|=3
=>x=3 hoặc x=-3
|x-1|+(-3)=17
|x-1|=17+3
|x-1|=20
x-1=20 hoặc x-1=-20
=>x=21 hoặc x=-19
|x|-(-4)=3
|x|=3-4
|x|=-1
=> x thuộc TH rỗng
(-x+31)-39=-69+1
-8-x=-68
x=-8-(-68)
x=60
-129-(35-x)=55
35-x=-129-55
35-x=-184
x=35+184
x=219
chúc bạn học tốt nha
ngay chỗ 4 phút trước (13:07)
Là tại thời gian mình làm nha còn 20 phút để làm các bn giúp nha!!!!
1. x + (-7) = -20
=> x = -20 - (-7)
=> x = -20 + 7
=> x = -13
Vậy x = -13
2. x + (-15) = 5
=> x = 5 - (-15)
=> x = 5 + 15
=> x = 20
3. (-95) + x = 10
=> x = 10 - (-95)
=> x = 10 + 95
=> x = 105
4. 8+ x = 12
=> x = 12 - 8
=> x = 4
5. x + (-45) = -62 + 17
=> x + (-45) = -45
=> x = -45 - (-45)
=> x = -45 + 45
=> x = 0
6 . x + 29 = |-43| + (-43)
=> x + 29 = 43 + (-43)
=> x + 29 = 0
=> x = 0 - 29
=> x = -29
7 . 43 + (9 - 21) = 317 - (x + 317)
=> 43 + (-12) = 317 - x - 317
=> 31 = 317 - x - 317
=> 317 - x - 317 = 31
=> 317 - x = 31 + 317
=> 317 - x = 348
=> x = 317 - 348
=> x = -31
Mỏi tay quá , bn tự làm nốt nha :)
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}
Bài 1: Tính hợp lí:
a) (-2) + 7 + (-12) + 17 + ...+ (-52) + 57
= [(-2) + 7] + [(-12) + 17] +... + [(-52) + 57]
= 5 + 5 + 5 + 5 + 5 + 5 = 5 . 6
= 30
b) (-30) + (-29) +...+ 48 + 49 + 50
= [(-30) + 30] + [(-29) + 29] +...+ 0 + 31 + 32 +...+ 49 + 50
= 0 + 0 +...+ 0 + 31 + 32 +...+ 50
= 0 + {[(50 -31) : 1 + 1] : 2} . (31 + 50)
= 0 + 810
= 810
Bài 2 : Tìm x:
a) 43 + (9 - 21) = 317 - (x + 317)
43 + (-12) = 317 - (x + 317)
31 = 317 - (x + 317)
317 - (x + 317) = 31
x + 317 = 317 - 31
x + 317 = 286
x = 286 - 317
x = -31
b) (15 - 2) + (x - 12) = 7 - (-5 + x)
15 - 2 + x - 12 = 7 + 5 - x
15 - 12 - x + x = 12 - x
15 - 12 = 12 - x
3 = 12 - x
12 - x = 3
x = 12 - 3
x = 9