VH
1
K
Khách
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25 tháng 10 2021
\(1,\Leftrightarrow7x=42\Leftrightarrow x=6\\ 2,\Leftrightarrow36-4x=4\Leftrightarrow4x=32\Leftrightarrow x=8\\ 3,\Leftrightarrow3x=35\Leftrightarrow x=\dfrac{35}{3}\\ 4,\Leftrightarrow x-12=144\Leftrightarrow x=156\\ 5,\Leftrightarrow x-14=16\Leftrightarrow x=30\\ 6,\Leftrightarrow3x-24=\dfrac{148}{73}\Leftrightarrow3x=\dfrac{1900}{73}\Leftrightarrow x=\dfrac{1900}{219}\\ 7,\Leftrightarrow33+x=45\Leftrightarrow x=12\\ 8,Sai.đề\\ 9,\Leftrightarrow\left(x+9\right):2=39\Leftrightarrow x+9=78\Leftrightarrow x=69\\ 11,\Leftrightarrow2\left(x+7\right)=38\Leftrightarrow x+7=19\Leftrightarrow x=12\\ 13,\Leftrightarrow2\left(x-51\right)=66\Leftrightarrow x-51=33\Leftrightarrow x=84\)
25 tháng 10 2021
\(15,\Leftrightarrow x-19=9\Leftrightarrow x=28\\ 17,\Leftrightarrow\left(x-3\right):2=48\Leftrightarrow x-3=96\Leftrightarrow x=99\\ 19,\Leftrightarrow0x=46\Leftrightarrow x\in\varnothing\\ 8,Sai.đề\\ 14,\Leftrightarrow2x=209\Leftrightarrow x=\dfrac{209}{2}\\ 16,\Leftrightarrow2x+6=157\Leftrightarrow2x=151\Leftrightarrow x=\dfrac{151}{2}\\ 18,\Leftrightarrow5\left(x+4\right)=100\Leftrightarrow x+4=20\Leftrightarrow x=16\\ 20,\Leftrightarrow\left(3x-5\right)^3=27=3^3\Leftrightarrow3x-5=3\Leftrightarrow x=\dfrac{8}{3}\)
NN
1
NH
8 tháng 2 2023
b)
`15-3(3x+18)=36`
`=> 3(3x+18)=15-36`
`=> 3(3x+18)=-21`
`=> 3x+18=-21:3`
`=> 3x+18=-7`
`=> 3x=-7-18`
`=> 3x=-25`
`=> x=-25:3`
`=> x=-25/3`
c)
`-12+(3-x)=25`
`=>-12+3-x=25`
`=>-x=25+12-3`
`=>-x=34`
`=>x=-34`
d)
`100-90xx(x:2-1)=-10`
`=>90xx(x:2-1)=100-(-10)`
`=>90xx(x:2-1)=110`
`=>x:2-1=110:90`
`=>x:2-1=11/9`
`=>x:2=11/9 +1`
`=> x:2=20/9`
`=> x=20/9 xx2`
`=> x=40/9`
NA
31 tháng 10 2021
a.219 - 7(x+1) = 100
7(x+1) = 219 - 100
7(x+1) = 119
x + 1 = 119 : 7
x + 1 = 17
x = 17 - 1
x = 16
b. (3x - 6 ) . 3 = 36
3x - 6 = 36 : 3
3x - 6 = 12
3x = 12 + 6
3x = 18
x = 18 : 3
x = 6
c.716 - ( x-143) = 659
x-143 = 716 - 659
x-143 = 57
x = 57 + 143
x = 200
b. 30 - [4(x-2)+15] = 3
4(x-2) + 15 = 30 - 3
4(x-2)+15 = 27
4(x-2) = 27 - 15
4(x-2) = 12
x-2 = 12 : 4
x-2 = 3
x = 2 + 3 = 5
e.[(8x - 12) : 4] .33 = 36
[(8x - 12) : 4] . 27 = 729
(8x - 12) : 4 = 729 : 27 = 27
8x - 12 = 27 . 4 = 108
8x = 108 + 12 = 120
x = 120 : 8 = 15
31 tháng 10 2021
a) \(\Leftrightarrow7\left(x+1\right)=119\\ \Leftrightarrow x+1=17\\ \Leftrightarrow x=16\)
b) \(\Leftrightarrow9\left(x-2\right)=36\\ \Leftrightarrow x-2=4\\ \Leftrightarrow x=6\)
c) \(\Leftrightarrow x-143=57\\ \Leftrightarrow x=200\)
d) \(\Leftrightarrow4\left(x-2\right)+15=27\\ \Leftrightarrow4\left(x-2\right)=12\\ \Leftrightarrow x-2=3\\ \Leftrightarrow x=5\)
e) \(\Leftrightarrow\left(2x-3\right).4:4=3^3\\ \Leftrightarrow2x-3=27\\ \Leftrightarrow2x=24\\ \Leftrightarrow x=12\)
DT
1
TV
1 tháng 4 2016
Ta có S=1/2^2+1/3^2+1/4^2+...+1/9^2
<1/2²+1/2*3+1/3*4+....+1/8*9
=1/2²+1/2-1/3+1/3-1/4+....+1/8-1/9
=1/4+1/2-1/9=23/36<32/36=8/9 (♪)
Ta lại có S=1/2^2+1/3^2+1/4^2+...+1/9^2
>1/2²+1/3*4+1/4*5+....+1/9*10
=1/2²+1/3-1/4+1/4-1/5+........+1/9-1/10
=1/2²+1/3-1/10
=19/20>8/20=2/5 ( ♫)
Từ (♪)( ♫) cho ta đpcm
14 tháng 8 2017
a, \(219-7\left(X+1\right)=100\)
\(\Rightarrow219-7X-7=100\)
\(\Rightarrow7X=219-7-100=112\)
\(\Rightarrow X=112:7=16\)
b,\(\left(3X-6\right)x3=3^4\)
\(\Rightarrow3X-6=81:3=27\)
\(\Rightarrow3X=27+6=33\)
\(\Rightarrow X=33:3=11\)
c,\(3636:\left(12X-91\right)=36\)
\(\Rightarrow12X-91=3636:36=101\)
\(\Rightarrow12X=101+91=192\)
\(\Rightarrow X=192:12=16\)
Đúng luôn nên...hằng ngày k cho mk 3 lần, bao h đủ 100 lần thì tui nhé
SS
2
DP
14 tháng 7 2017
Sửa đề : \(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{x\left(x+1\right)}=\frac{98}{100}\)
\(\Leftrightarrow\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}=\frac{98}{100}\)
\(\Leftrightarrow\frac{2-1}{1\times2}+\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}+....+\frac{\left(x+1\right)-x}{x\left(x+1\right)}=\frac{98}{100}\)
\(\Leftrightarrow\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+....+\frac{1}{x}-\frac{1}{\left(x+1\right)}=\frac{98}{100}\)
\(\Leftrightarrow\frac{1}{1}-\frac{1}{\left(x+1\right)}=\frac{98}{100}\)
\(\Leftrightarrow\frac{1}{\left(x+1\right)}=\frac{1}{1}-\frac{98}{100}\)
\(\Leftrightarrow\frac{1}{\left(x+1\right)}=\frac{1}{50}\)
\(\Leftrightarrow x=50-1=49\)
14 tháng 7 2017
Sửa đề: \(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{x\left(x+1\right)}=\frac{98}{100}\)
(=) \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}=\frac{98}{100}\)
(=)\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{98}{100}\)
(=)\(1-\frac{1}{x+1}=\frac{98}{100}\)
(=)\(\frac{1}{x+1}=1-\frac{98}{100}\)
(=)\(\frac{1}{x+1}=\frac{1}{50}\)=> \(x+1=50\)
\(x=50-1\)
\(x=49\)
T_i_c_k cho mình nha,thanks you so much!
=432{50x20}+50
=432x1000+50
=432000+50
=432050