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a: x*3/4=1/5
=>x=1/5:3/4=1/5*4/3=4/15
b: x*3/7=2/5
=>x=2/5:3/7=2/5*7/3=14/15
c: 1/3+2/9=2/12x
=>1/6x=3/9+2/9=5/9
=>x=5/9*6=30/9=10/3
d: 4/15*x-2/3=1/5
=>4/15*x=2/3+1/5=10/15+3/15=13/15
=>4x=13
=>x=13/4
e: x:1/7=2/3
=>x=2/3*1/7=2/21
f: 1/9:x=7/3
=>x=1/9:7/3=1/9*3/7=3/63=1/21
j: 1/4+5/12=8/3:x
=>8/3:x=3/12+5/12=8/12=2/3
=>x=4
h: =>7/4:x=1/5+1/2=7/10
=>x=7/4:7/10=10/4=5/2
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\(a,\dfrac{-1}{8}=\dfrac{3}{x}\\ \dfrac{3}{-24}=\dfrac{3}{x}\\ x=-24\\ b,\dfrac{x}{3}=\dfrac{3}{x}\\ x.x=3.3\\ x^2=9\\ x=\pm3\\ c,\dfrac{3}{4}.x=1\dfrac{1}{2}\\ \dfrac{3}{4}.x=\dfrac{3}{2}\\ x=\dfrac{3}{2}:\dfrac{3}{4}\\ x=2\\ d,x-\dfrac{3}{10}=\dfrac{7}{15}:\dfrac{3}{5}\\ x-\dfrac{3}{10}=\dfrac{7}{9}\\ x=\dfrac{7}{9}+\dfrac{3}{10}\\ x=\dfrac{97}{90}\\ e,\dfrac{-4}{7}-x=\dfrac{-8}{3}.\dfrac{3}{7}\\ \dfrac{-4}{7}-x=\dfrac{-8}{7}\\ x=\dfrac{-4}{7}+\dfrac{8}{7}\\ x=\dfrac{4}{7}\\ \)
5:
a: \(3^{2n}=\left(3^2\right)^n=9^n\)
\(\left(2^{3n}\right)=\left(2^3\right)^n=8^n\)
=>\(3^{2n}>2^{3n}\)
b: \(199^{20}=\left(199^4\right)^5=1568239201^5\)
\(2003^{15}=\left(2003^3\right)^5=8036054027^5\)
mà \(1568239201< 8036054027\)
nên \(199^{20}< 2003^{15}\)
4: \(100< 5^{2x-1}< 5^6\)
mà \(25< 100< 125\)
nên \(125< 5^{2x-1}< 5^6\)
=>3<2x-1<6
=>4<2x<7
=>2<x<7/2
mà x nguyên
nên x=3
Tìm x
a) 4/5 ( x - 1/3) - \(3\dfrac{1}{2}\)= 50%
b) \(8\dfrac{3}{5}\cdot x-2\dfrac{1}{5}\cdot x=16\%\)
a) \(\dfrac{4}{5}\left(x-\dfrac{1}{3}\right)-3\dfrac{1}{2}=50\%\)
\(\dfrac{4}{5}x-\dfrac{4}{15}-\dfrac{7}{2}=\dfrac{1}{2}\)
\(\dfrac{4}{5}x=\dfrac{1}{2}+\dfrac{7}{2}+\dfrac{4}{15}\)
\(\dfrac{4}{5}x=\dfrac{64}{15}\)
\(x=\dfrac{64}{15}:\dfrac{4}{5}\\ x=\dfrac{16}{3}\)
b) \(8\dfrac{3}{5}.x-2\dfrac{1}{5}.x=16\%\)
\(\dfrac{43}{5}x-\dfrac{11}{5}x=\dfrac{4}{25}\)
\(\dfrac{32}{5}x=\dfrac{4}{25}\)
\(x=\dfrac{4}{25}:\dfrac{32}{5}\)
\(x=\dfrac{1}{40}\)
2/10 = 1/5
=> x = 1
3/5 x = 1/4 + 1/3
3/5x = 7/12
x = 7/12 : 3/5
x = 35/36
1/5: x = 2/35
x = 1/5 : 2/35
x = 7/2
` 8/23 . 46/24 =1/3 .x`
`=>8/23 . 23/12 =1/3 . x`
`=> 1/3 . x=2/3`
`=>x=2/3 : 1/3`
`=>x=2/3 . 3`
`=> x= 6/3`
`=>x=2`
`----`
`1/5 : x= 1/5-1/7`
`=>1/5 : x= 7/35 - 5/35`
`=> 1/5 :x= 2/35`
`=>x= 1/5 : 2/35`
`=>x=1/5 . 35/2`
`=>x=7/2`
`----`
`4/9 - (x-1/2)^2 =1/3`
`=> (x-1/2)^2 =4/9-1/3`
`=> (x-1/2)^2 =4/9- 3/9`
`=> (x-1/2)^2 =1/9`
`=> (x-1/2)^2 = (+- 1/3)^2`
`@ TH1`
`x-1/2=1/3`
`=>x=1/3+1/2`
`=>x= 2/6 + 3/6`
``=>x= 5/6`
`@ TH2`
`x-1/2=-1/3`
`=>x=-1/3 +1/2`
`=>x= -2/6 + 3/6`
`=>x=1/6`
`----`
`3,2 . x-(4/5+2/3) : 3 2/3 = 7/10`
`=> 3,2 . x-22/15 : 11/3 = 7/10`
`=> 3,2 . x-22/15 = 7/10 . 11/3`
`=> 3,2 . x-22/15 =77/30`
`=> 3,2 .x= 77/30 + 22/15`
`=> 3,2 .x=121/30`
`=>x= 121/30. 5/16`
`=>x= 121/96`
a: =>x/27+1=-2/3
=>x/27=-5/3
=>x=-45
b: \(\Leftrightarrow x-4=\dfrac{2}{5}:\dfrac{20}{21}=\dfrac{2}{5}\cdot\dfrac{21}{20}=\dfrac{42}{100}=\dfrac{21}{50}\)
=>x=221/50
c: \(\Leftrightarrow x+\dfrac{2}{3}=\dfrac{4}{60}=\dfrac{1}{15}\)
=>x=1/15-2/3=1/15-10/15=-9/15=-3/5
d: \(\Leftrightarrow x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{15}{14}\cdot\dfrac{21}{20}\)
=>\(x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{3}{2}\cdot\dfrac{3}{4}=\dfrac{1}{5}-\dfrac{9}{8}=\dfrac{-37}{40}\)
=>x=-37/24
e: =>-3/7x=84/45
=>x=-196/45
f: =>11/10x=-2/3
=>x=-20/33
Bài 3:
Gọi số nhóm là x
Theo đề, ta có: \(x\in\left\{1;2;3;4;6;9;12;18;36\right\}\)
mà 2<x<6
nên \(x\in\left\{3;4\right\}\)
Vậy: Có 2 cách chia nhóm
a) 25 - x = 12 + 6 =18
x=25-18=7 Vậy x=7
b) 7 + 2 x ( x -3 ) = 11
2.(x-3)=11-7=4
x-3=4:2=2
x=3+2=5
c) 102 : ( 2.x + 13) : 4) = 6
(2.x+13):4=102:6=17
2.x+13=17.4=68
2.x=68-13=55
x=27,5 Vậy x=27,5
Bài 3:
Gọi số nhóm là x
Theo đề, ta có: x∈{1;2;3;4;6;9;12;18;36}x∈{1;2;3;4;6;9;12;18;36}
mà 2<x<6
nên x∈{3;4}x∈{3;4}
Vậy: Có 2 cách chia nhóm
còn bài 1 chắc bn làm đc nha tick mk nha
a: =>x-2/5=3/4:1/3=3/4*3=9/4
=>x=9/4+2/5=45/20+8/20=53/20
b: =>x-2/3=7/3:4/5=7/3*5/4=35/12
=>x=35/12+2/3=43/12
c: 1/3(x-2/5)=4/5
=>x-2/5=4/5*3=12/5
=>x=12/5+2/5=14/5
d: =>2/3x-1/3-1/4x+1/10=7/3
=>5/12x-7/30=7/3
=>5/12x=7/3+7/30=77/30
=>x=77/30:5/12=154/25
e: \(\Leftrightarrow x\cdot\dfrac{3}{7}-\dfrac{2}{7}+\dfrac{1}{2}-\dfrac{5}{4}x+\dfrac{5}{2}=0\)
=>\(x\cdot\dfrac{-23}{28}=\dfrac{2}{7}-3=\dfrac{-19}{7}\)
=>x=19/7:23/28=76/23
f: =>1/2x-3/2+1/3x-4/3+1/4x-5/4=1/5
=>13/12x=1/5+3/2+4/3+5/4=257/60
=>x=257/65
i: =>x^2-2/5x-x^2-2x+11/4=4/3
=>-12/5x=4/3-11/4=-17/12
=>x=17/12:12/5=85/144
Giải:
a) \(2^5=4^x\)
\(\Rightarrow2^5=\left(2^2\right)^x\)
\(\Rightarrow2^5=2^{2x}\)
\(\Rightarrow2x=5\)
\(\Rightarrow x=\dfrac{5}{2}\)
b) \(2.4^2.8^3.16^4=8^x\)
\(\Rightarrow2.\left(2^2\right)^2.\left(2^3\right)^3.\left(2^4\right)^4=\left(2^3\right)^x\)
\(\Rightarrow2.2^4.2^9.2^{16}=2^{3x}\)
\(\Rightarrow2^{30}=2^{3x}\)
\(\Rightarrow3x=30\)
\(\Rightarrow x=30:3\)
\(\Rightarrow x=10\)
c) \(3^3:3^5=9^x\)
\(\Rightarrow3^{-2}=\left(3^2\right)^x\)
\(\Rightarrow3^{-2}=3^{2x}\)
\(\Rightarrow2x=-2\)
\(\Rightarrow x=-2:2\)
\(\Rightarrow x=-1\)
Chúc bạn học tốt!
a) Ta có: \(2^5=4^x\)
nên \(2^{2x}=2^5\)
\(\Leftrightarrow2x=5\)
hay \(x=\dfrac{5}{2}\)
b) Ta có: \(2\cdot4^2\cdot8^3\cdot16^4=8^x\)
\(\Leftrightarrow2^{3x}=2\cdot2^5\cdot2^9\cdot2^{16}=2^{31}\)
\(\Leftrightarrow3x=31\)
hay \(x=\dfrac{31}{3}\)
c) Ta có: \(3^3:3^5=9^x\)
\(\Leftrightarrow3^{-2}=3^{2x}\)
\(\Leftrightarrow2x=-2\)
hay x=-1
a ) x = − 4 5 − 1 2 ⇔ x = − 13 10 b ) x = − 3 4 − 2 3 ⇔ x = − 17 12 c ) − 3 5 : x = − 2 3 − 2 3 5 ⇔ − 3 5 : x = − 49 15 ⇔ x = − 3 5 : − 49 15 ⇔ x = 9 49
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