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`a,`
`31/23-(7/32+8/23)`
`=31/23-7/32-8/23`
`=(31/23-8/23)-7/32`
`=1-7/32=25/32`
`b,`
`38/45-(8/45-17/51-3/11)`
`=38/45-8/45+17/51+3/11`
`= (38/45-8/45)+17/51+3/11`
`=2/3+17/51+3/11`
`=1+3/11=14/11`
`c,`
`(1/3+12/67+13/41)-(79/67-28/41)`
`= 1/3+12/67+13/41-79/67+28/41`
`= 1/3+(12/67-79/67)+(13/41+28/41)`
`= 1/3+(-1)+1=1/3+(-1+1)=1/3+0=1/3`
`d,`
`1/5+(-1/6)+1/7+(-1/8)+1/9+1/8+(-1/7)+1/6+(-1/5)`
`= (1/5+ -1/5)+(-1/6+1/6)+(1/7+ -1/7)+(-1/8 +1/8)+1/9`
`= 0+0+0+0+1/9=1/9 .`
a: \(=\dfrac{4\cdot11\cdot3}{4\cdot9}\cdot\dfrac{1}{121}=\dfrac{11}{121}\cdot\dfrac{1}{3}=\dfrac{1}{33}\)
b: \(=\dfrac{7}{9}\left(\dfrac{3}{4}+\dfrac{1}{4}\right)=\dfrac{7}{9}\)
c: \(=\dfrac{-6}{7}-\dfrac{1}{7}+\dfrac{2}{11}+\dfrac{9}{11}+\dfrac{12}{17}=\dfrac{12}{17}\)
Bài 1:
a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)
b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)
c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)
d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)
hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)
e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)
hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)
1/ -7264 + (1543 + 7264)
=-7264 + 1543 + 7264=1543
2/ (144 – 97) – 144
=144-97-144=-97
3/ (-145) – (18 – 145)(Vì có dấu trừ ở trước ngoặc nên p đổi dấu)
=-145-18+145=-18
4/ 111 + (-11 + 27)
=111-11+27=137
120 - { 300: [ 40 - (2.562 - 262.5)] + 10}
= 120 - { 300 : [ 40 - (-186)] + 10}
= 120 - {300 : 226 + 10}
= 120 - \(\dfrac{1280}{113}\)
= \(\dfrac{12280}{113}\)
a: =(1-2-3+4)+(5-6-7+8)+...+(21-22-23+24)
=0+0+...+0
=0
b: =-7111+53+711-153=-6400-100=-6500
c: =-43(-1-296+296)=-43*(-1)=43
Bài 2:
a: =>x-35=-23
=>x=12
b: =>|x-8|=13
=>x-8=13 hoặc x-8=-13
=>x=21 hoặc x=-5
Bài 1:
a: =42-98-42+12-12=-98
b: =10x4x3x(-25)=40x(-25)x3=-1000x3=-3000
a =143
b = 2510
c 28 x 73 = 2044
cái câu c tính nhẩm chết liền
d [ 1700 - 340 +17 ] : 17 = 81
2 . Tìm x
a 7 . [ x - 3 ] - 6 = 1
7 . [ x - 3 ] = 1+6
7 . [ x - 3 ] = 7
x - 3 = 7 : 7
x - 3 =1
x=3+1=4
b
[x+5] .2:11=6
[x+5] x 2 = 6 x 11
[ x + 5 ] x 2 = 66
x+2=66:2
x+2=33
x=33-2=31
Bài 1
a, \(45+98=143\)
b, \(2605-95=2510\)
c,\(28.73+28\)
\(=28.\left(73+1\right)\)
\(=28.74\)
\(=2072\)
d,\(\left[1700-340+17\right]:17\)
\(=1700:17-340:17+17:17\)
\(=100-20+1\)
\(=81\)
Bài 2
a, \(7.\left(x-3\right)-6=1\)
\(\Leftrightarrow7.\left(x-3\right)=7\)
\(\Leftrightarrow x-3=1\)
\(\Leftrightarrow x=4\)
b, \(\left(x+2\right).2:11=6\)
\(\Leftrightarrow\left(x+2\right).2=66\)
\(\Leftrightarrow x+2=33\)
\(\Leftrightarrow x=31\)