b) \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

\(\dfrac{1}{4}:x=\dfrac{2}{5}-\dfrac{3}{4}\)

\(\dfrac{1}{4}:x=\dfrac{7}{20}\)

\(x=\dfrac{1}{4}:\dfrac{7}{20}=\dfrac{5}{7}\)

\(\left|x-3\right|=\dfrac{1}{2}\)

\(x-3=\pm\dfrac{1}{2}\)

c) \(1\dfrac{1}{3}:0,8=\dfrac{2}{3}:0,1x\)

\(\dfrac{5}{3}=\dfrac{2}{3}:0,1x\)

\(0,1x=\dfrac{2}{3}:\dfrac{5}{3}\)

\(0,1x=0,4\)

\(x=0,4:0,1=4\)

a: \(\Leftrightarrow x^2=900\)

=>x=30 hoặc x=-30

b: \(\Leftrightarrow\dfrac{2}{3}:\left(-0.1x\right)=\dfrac{4}{3}:\dfrac{-2}{25}=-\dfrac{4}{3}\cdot\dfrac{25}{2}=-\dfrac{100}{6}=\dfrac{-50}{3}\)

=>0,1x=2/3:50/3=2/3x3/50=1/25

=>1/10x=1/25

hay x=1/25:1/10=10/25=2/5

d: \(\Leftrightarrow x^2=\dfrac{144}{25}\)

=>x=12/5 hoặc x=-12/5

1)

a) \(\frac{x}{6}\)= \(\frac{7}{3}\)

\(\Rightarrow\)x.3=6.7

\(\Rightarrow\)x.3=42

\(\Rightarrow\)x   =42:3

\(\Rightarrow\)x   =14

b) làm tương tự như câu a

c) làm tương tự như câu

 d) làm tương tư như câu a nhưng hơi phúc tạp một chút là bn phải đổi ra từ hỗn số ra phân số hoặc số nguyên

e) tương tự câu d

f) làm tương tự như câu d

2)

a) 3x:\(\frac{27}{10}\)=\(\frac{1}{3}\): \(2\frac{1}{4}\)

3x: \(\frac{27}{10}\) = \(\frac{1}{3}\): \(\frac{9}{4}\)

3x: \(\frac{27}{10}\) = \(\frac{4}{27}\)

3x       = \(\frac{4}{27}\). \(\frac{27}{10}\)

3x       = \(\frac{2}{5}\)

 x        = \(\frac{2}{5}\):  3

x         = \(\frac{2}{15}\)

Các câu còn lại bn làm tương tự như câu a nha

3) 

Làm tương tự như bài 2 nha

 mik khuyên bn nếu bn giải bài thì bn nên đổi ra cùng một kiểu số thì tốt hơn như số số thập phân thì thập phân hết ấy

Cuối cùng chúc bn học giỏi

\(a,\dfrac{x}{6}=\dfrac{7}{3}\Rightarrow x=\dfrac{6.7}{3}\Rightarrow x=14\)

\(b,\dfrac{20}{x}=\dfrac{-12}{15}\Rightarrow x=\dfrac{20.15}{-12}\Rightarrow x=-25\)

\(c,\dfrac{-15}{35}=\dfrac{27}{x}\Rightarrow x=\dfrac{35.27}{-15}\Rightarrow x=-63\)

\(d,\dfrac{\dfrac{4}{5}}{1\dfrac{2}{5}}=\dfrac{2\dfrac{2}{5}}{x}\Rightarrow\dfrac{\dfrac{4}{5}}{\dfrac{7}{5}}=\dfrac{\dfrac{12}{5}}{x}\Rightarrow x=\dfrac{\dfrac{7}{5}.\dfrac{12}{5}}{\dfrac{4}{5}}\Rightarrow x=\dfrac{\dfrac{84}{25}}{\dfrac{4}{5}}\Rightarrow x=\dfrac{21}{5}\)

\(e,\dfrac{x}{1\dfrac{1}{4}}=\dfrac{5}{2}\Rightarrow\dfrac{x}{\dfrac{5}{4}}=\dfrac{5}{2}\Rightarrow x=\dfrac{5}{2}.\dfrac{5}{4}\Rightarrow x=\dfrac{25}{8}\)

\(f,\dfrac{\dfrac{1}{2}}{1\dfrac{1}{4}}=\dfrac{x}{3\dfrac{1}{3}}\Rightarrow\dfrac{\dfrac{1}{2}}{\dfrac{5}{4}}=\dfrac{x}{\dfrac{10}{3}}\Rightarrow x=\dfrac{\dfrac{10}{3}.\dfrac{1}{2}}{\dfrac{5}{4}}\Rightarrow x=\dfrac{\dfrac{5}{3}}{\dfrac{5}{4}}\Rightarrow x=\dfrac{4}{3}\)

a,\(1.25:0.2=1.25:0.1x\Rightarrow1.25:0.1x=\dfrac{25}{4}\Rightarrow0.1x=\dfrac{1}{5}\Rightarrow x=2\)

b,\(3.8:2x=\dfrac{1}{4}:2\dfrac{2}{3}\Rightarrow3.8:2x=\dfrac{3}{32}\Rightarrow2x=\dfrac{608}{15}\Rightarrow x=\dfrac{304}{15}\)

\(a,3x:2,7=\dfrac{1}{3}:2\dfrac{1}{4}\Rightarrow3x:2,7=\dfrac{4}{27}\Rightarrow3x=\dfrac{2}{5}\Rightarrow x=\dfrac{2}{15}\)

b,\(3:0.4x=1:0.01\Rightarrow3:0.4x=100\Rightarrow0.4x=\dfrac{3}{100}\Rightarrow x=\dfrac{3}{40}\)

c,

\(4,5:0,3=2,25:0.1x\Rightarrow2.25:0.1x=15\Rightarrow0.1x=\dfrac{3}{20}\Rightarrow x=\dfrac{3}{2}\)

d,\(x:27=-2:3,6\Rightarrow x:27=\dfrac{-5}{9}\Rightarrow x=-15\)

a)\(3,8:\left(2x\right)=\dfrac{1}{4}:2\dfrac{2}{3}\)

\(2x=3,8:\dfrac{3}{32}\)

\(x=\dfrac{608}{15}:2\)

\(x=\dfrac{304}{15}\)

b)\(\left(0,25x\right):3=\dfrac{5}{6}:0,125\)

\(0,25x=\dfrac{20}{3}\times3\)

\(x=20:0,25\)

\(x=80\)

c) \(0,01:2,5=\left(0,75\times x\right):0,75\)

\(0,004=0,75\times x:0,75\)

\(0,004=x\times0,75:0,75\)

\(0,004=x\times1\)

\(0,004=x\)

\(\Rightarrow x=0,004\)

d)\(1\dfrac{1}{3}:0,8=\dfrac{2}{3}:\left(0,1x\right)\)

\(\dfrac{5}{3}=\dfrac{2}{3}:0,1\times x\)

\(\dfrac{5}{3}=\dfrac{20}{3}\times x\)

\(\Rightarrow x=\dfrac{20}{3}:\dfrac{5}{3}\)

\(x=4\)

a) \(x=20\dfrac{4}{15}.\)

b) \(x=80\)

c) \(x=0,004\)

d) \(x=4.\)

bài 1) ta có : \(\dfrac{2x-y}{x+y}=\dfrac{2}{3}\Leftrightarrow2\left(x+y\right)=3\left(2x-y\right)\)

\(\Leftrightarrow2x+2y=6x-3y\Leftrightarrow4x=5y\Leftrightarrow\dfrac{x}{y}=\dfrac{5}{4}\)

vậy \(\dfrac{x}{y}=\dfrac{5}{4}\)

bài 1

\(\dfrac{2x-y}{x+y}=\dfrac{2}{3}\Leftrightarrow\dfrac{2.\dfrac{x}{y}-1}{\dfrac{x}{y}+1}=\dfrac{2.\dfrac{x}{y}+2-3}{\dfrac{x}{y}+1}=2-\dfrac{3}{\dfrac{x}{y}+1}=\dfrac{2}{3}\)

\(2-\dfrac{2}{3}=\dfrac{4}{3}=\dfrac{3}{\dfrac{x}{y}+1}\)

\(\left(\dfrac{x}{y}+1\right)=\dfrac{9}{4}\Rightarrow\dfrac{x}{y}=\dfrac{9}{4}-\dfrac{4}{4}=\dfrac{5}{4}\)

3) \(A=\dfrac{8^{10}+4^{10}}{8^4+4^{11}}=\dfrac{2^{30}+2^{20}}{2^{12}+2^{22}}\)

\(=\dfrac{2^{20}\left(2^{10}+1\right)}{2^{12}\left(2^{10}+1\right)}=\dfrac{2^{20}}{2^{12}}\)

\(=2^{20-12}=2^8\)

Vậy \(A=2^8\)

a: \(\Leftrightarrow\left(\dfrac{1}{4}\cdot x\right):3=\dfrac{5}{6}:\dfrac{1}{8}=\dfrac{5}{6}\cdot8=\dfrac{40}{6}=\dfrac{20}{3}\)

=>1/4x=20

=>x=80

b: \(\Leftrightarrow\dfrac{2}{3}:0.1x=\dfrac{4}{3}\cdot\dfrac{5}{4}=\dfrac{5}{3}\)

=>\(x\cdot\dfrac{1}{10}=\dfrac{2}{3}:\dfrac{5}{3}=\dfrac{2}{5}\)

=>x=2/5:1/10=2/5x10=4

Bài 1: Giải các phương trình sau:

a) 3(2,2-0,3x)=2,6 + (0,1x-4)

<=> 6.6 - 0.9x = 2,6 + 0,1x - 4

<=> - 0.9x - 0,1x = -6.6 -1,4

<=> -x = -8

<=> x = 8

Vậy x = 8

b) 3,6 -0,5 (2x+1) = x - 0,25(22-4x)

<=> 3,6 - x - 0,5 = x - 5,5 + x

<=> - x - 3,1 = -5,5

<=> - x = -2.4

<=> x = 2.4

Vậy  x = 2.4

a: \(x=\left(-\dfrac{2}{3}\right)^5:\left(-\dfrac{2}{3}\right)^2=\left(-\dfrac{2}{3}\right)^3=-\dfrac{8}{27}\)

b: =>x-1/2=1/3

=>x=5/6

c: =>2/3x-1=0 hoặc 3/4x+1/2=0

=>x=3/2 hoặc x=-1/2:3/4=-1/2*4/3=-4/6=-2/3

d =>4/9:x=10/3:9/4=10/3*4/9=40/27

=>x=4/9:40/27=4/9*27/40=108/360=3/10