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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
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
\(g,\left[119-\left(3^3-10\right)\right].x=2448\\ \Leftrightarrow\left[119-\left(27-10\right)\right].x=2448\\ \Leftrightarrow\left[119-27+10\right].x=2448\\ \Leftrightarrow102.x=2448\\ \Leftrightarrow x=\dfrac{2448}{102}=24\\ h,\left[\left(10-x\right).2+51\right]:3-2=3\\ \Leftrightarrow\left[\left(10-x\right).2+51\right]:3=3+2=5\\ \Leftrightarrow\left[\left(10-x\right).2+51\right]=5.3=15\\ \Leftrightarrow\left(10-x\right).2=15-51=-36\\ \Leftrightarrow10-x=\dfrac{-36}{2}=-18\\ \Leftrightarrow x=10-\left(-18\right)=28\\ i,\left(x-12\right)-15=20-\left(17+x\right)\\ \Leftrightarrow x-12-15=20-17-x\\ \Leftrightarrow x+x=20-17+12+15\\ \Leftrightarrow2x=30\\ \Leftrightarrow x=\dfrac{30}{2}=15\)
\(k,-12-\left|13-x\right|=-21\\ \Leftrightarrow\left|13-x\right|=-12-\left(-21\right)=-12+21=9\\ \Leftrightarrow\left[{}\begin{matrix}13-x=9\\13-x=-9\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=13-9=4\\x=13-\left(-9\right)=13+9=22\end{matrix}\right.\)
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
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
2017-{5^2.2^2-11[7^2-5.2^3+8(11^2-121)]}=
=2017-{25.4-11[49-5.8+8(121-121)]}=
= 2017-{100-11[49-40+0]}=2017-{100-11.9}=2017-1=2016
\(2017-\left\{5^2.2^2-11.\left[7^2-5.2^3+8\left(11^2-121\right)\right]\right\}\)\(=1017-\left\{100-11\left[49-40+8\left(121-121\right)\right]\right\}\)
\(=2017-\left\{100-11\left[9+8.0\right]\right\}\)
\(=2017-\left\{100-11.9\right\}\)
\(=2017-\left(100-99\right)=1017-1=2016\)
g: \(=-418+218+\left[-118+131\right]-2017\)
\(=-200-2017-13\)
=-200-2030
=-2230
h: \(=5+5+...+5=5\cdot6=30\)
i: \(=\left(-30+30\right)+\left(-29+29\right)+...+31+32+...+49+50\)
\(=31+32+...+49+50\)
Số số hạng là:
(50-31):1+1=19+1=20(số)
Tổng là: \(81\cdot\dfrac{20}{2}=810\)
sai r bn ơi