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a: =>31-x-39=-58
=>-8-x=-58
=>x+8=58
hay x=50
b: =>-129-35+x=55
=>x-164=55
hay x=219
c: =>|x-7|=-37+127=90
=>x-7=90 hoặc x-7=-90
=>x=97 hoặc x=-83
d: =>|x-14|<2
=>x-14>-2 và x-14<2
=>12<x<16
e: =>315-x-315=43-12
=>-x=31
hay x=-31
f: =>|x-4|=4
=>x-4=4 hoặc x-4=-4
=>x=8 hoặc x=0
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a: =>25-25+x=12+42-65
=>x=-11
b: =>|x+3|=4
=>x+3=4 hoặc x+3=-4
=>x=1 hoặc x=-7
c: =>x+17=13
hay x=-4
d: =>x+25-x=13-x
=>13-x=25
hay x=-12
e: =>15-30-x=x-(27-8)
=>-15-x=x-19
=>-x-x=-19+15
=>-2x=-4
hay x=2
f: \(\Leftrightarrow\left(12x-64\right)=4\cdot8=32\)
=>12x=96
hay x=8
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\(g,\left[119-\left(3^3-10\right)\right].x=2448\\ \Leftrightarrow\left[119-\left(27-10\right)\right].x=2448\\ \Leftrightarrow\left[119-27+10\right].x=2448\\ \Leftrightarrow102.x=2448\\ \Leftrightarrow x=\dfrac{2448}{102}=24\\ h,\left[\left(10-x\right).2+51\right]:3-2=3\\ \Leftrightarrow\left[\left(10-x\right).2+51\right]:3=3+2=5\\ \Leftrightarrow\left[\left(10-x\right).2+51\right]=5.3=15\\ \Leftrightarrow\left(10-x\right).2=15-51=-36\\ \Leftrightarrow10-x=\dfrac{-36}{2}=-18\\ \Leftrightarrow x=10-\left(-18\right)=28\\ i,\left(x-12\right)-15=20-\left(17+x\right)\\ \Leftrightarrow x-12-15=20-17-x\\ \Leftrightarrow x+x=20-17+12+15\\ \Leftrightarrow2x=30\\ \Leftrightarrow x=\dfrac{30}{2}=15\)
\(k,-12-\left|13-x\right|=-21\\ \Leftrightarrow\left|13-x\right|=-12-\left(-21\right)=-12+21=9\\ \Leftrightarrow\left[{}\begin{matrix}13-x=9\\13-x=-9\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=13-9=4\\x=13-\left(-9\right)=13+9=22\end{matrix}\right.\)
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e: =(2004-2004)+(54-54)+(-15)=-15
f: =(-45789x2)-(357-57)=-91578-300=-91878
g: =(1259+1259)-(1409-1409)-12=2506
h: =(2750x2)-1229+438+29+438
=5500-1200+876
=5176
i: =-5+(-37+37)+(151+151)-45
=-50+302
=252
k: =(53-53)+(-145+145)-(359+259)=-618
e)2004-15+54-2004-54=(2004-2004)+(54-54)-15=-15
f)-45789-357-45789+57=(-45789-45789)-(357-57)=-91578-300=-91878
g)1259-1409-12+1259+140=(1259+1259)+(-1409+1409)-12=2518-12=2506
h)2750-1229+2750-(-438-29-438)=(2750+2750)-1229+438+29+438=5500-(1229-29)+(438+438)=5500-1200+876=5176
i)-5+-37-45+151--37=-5-37-45+151+37=(-5-45)+(-37+37)+151=-50+151=101
k)53-145-359-53+145-259=(53-53)+(-145+145)+(-359-259)=-618
l)-81-132-547+181-132-53=(-81+181)-(547+53)-(132+132)=100-600-264=-764
m)50-2016+50-118+2016-18=(50+50)+(-2016+2016)-(118+18)=100-136=-36
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q: =-223+105-2x172+223=105-344=-239
p: =173-536+173-526=-716
n: =(254+254)+(549-49)+(-175-75)
=508+500-250
=508+250
=758
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a, -22 < x < 23
\(=>x\in\left\{-21;-20;...;22\right\}\)
Tổng của các số nguyên x trên:
-21 + (-20) + ... + 22
= ( -21 + 21 ) + ( -20 + 20 ) + ... + 22
= 0 + 0 + ... + 22
= 22
b, -36 < x < 34
\(=>x\in\left\{-35;-34;-33;...;33\right\}\)
Tổng của các số nguyên x trên :
-35 + ( -34 ) + ( -33 ) + ... + 33
= -35 + ( - 34 ) + ( -33 + 33 ) + ... + ( -1 ) + 1 + 0
= -35 + ( -34 ) + 0 + ... + 0 + 0
= -69
Vậy ........
a) -22 < x < 23
-> x thuộc { -22, -21-.....,21,22,23}
-> Có : (-22 +22)+(21+-21) +........(1+-1) +0 +23= 23
b)-36<x<34
->x thuộc {-36;-35;-34;.......;34}
->Có : (-34+34)+(-33+33)+.......+(1+-1)+0-36-35= -71
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a) 48=24.3
16=24
BCNN(48;16)=24.3=48
BC(48;16)=B(48)= { bạn tự tìm nhé}
Ta có 48=24.3
16=24
Suy ra BCNN(48;16)=24.3=48
Mà BC(48;16)=B(48)={48;96;144;192;240;....}
Bài 1:
a) \(215+\left(-38\right)-\left(-58\right)+90-85\)
\(=215-38+58+90-85\)
\(=\left(215-85\right)+\left(-38+58\right)+90\)
\(=130+20+90\)
\(=240\)
b) \(917-\left(417-65\right)\)
\(=917-417+75\)
\(=500+75\)
\(=575\)
c) \(31-\left[26-\left(2017+35\right)\right]\)
\(=31-\left(26-2017-35\right)\)
\(=31-26+2017+35\)
\(=\left(31+35-26\right)+2017\)
\(=40+2017\)
\(=2057\)
d) \(54+\left(-37+10-54+67\right)\)
\(=54-27+10-54+67\)
\(=\left(54-54\right)+\left(-27+67\right)+10\)
\(=0+40+10\)
\(=50\)
e) \(\left(326-43\right)+\left(174-57\right)\)
\(=326-43+174-57\)
\(=\left(326+174\right)-\left(43+57\right)\)
\(=500-100\)
\(=400\)
f) \(\left(351-875\right)-\left(125-149\right)\)
\(=351-875-125+149\)
\(=\left(351+149\right)-\left(875+125\right)\)
\(=500-1000\)
\(=-500\)
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