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19 tháng 9 2017

\(\dfrac{5}{6}x-\dfrac{3}{4}=\dfrac{-1}{4}+\dfrac{2}{3}\)

\(\Leftrightarrow\dfrac{5}{6}x=\dfrac{7}{6}\)

\(\Rightarrow x=\dfrac{7}{5}\)

b) \(-1\dfrac{1}{2}-\dfrac{2}{3}x=\dfrac{5}{6}-\left(\dfrac{-2}{5}\right)\)

\(\Leftrightarrow\dfrac{2}{3}x=-\dfrac{41}{15}\)

\(\Rightarrow x=-\dfrac{41}{10}\)

c) \(\left(\dfrac{4}{5}:x+1,5\right):\dfrac{2}{3}=-1,5\)

\(\Leftrightarrow\dfrac{8+15x}{10x}.\dfrac{3}{2}=\dfrac{-3}{2}\)

\(\Leftrightarrow\dfrac{24+45x}{20x}=\dfrac{-3}{2}\)

\(\Leftrightarrow-60x=48+90x\)

\(\Rightarrow x=-0,32\)

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

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

\(\Rightarrow16x-8=3-12x\)

\(\Rightarrow x=\dfrac{11}{28}\)

\(A=\left(\dfrac{1}{3}+\dfrac{3}{5}+\dfrac{1}{15}\right)-\left(\dfrac{3}{4}+\dfrac{2}{9}+\dfrac{1}{36}\right)+\dfrac{1}{64}\)

\(=\dfrac{5+9+1}{15}-\dfrac{27+8+1}{36}+\dfrac{1}{64}\)

=1/64

 

a: \(\dfrac{2.75}{x}=\dfrac{0.4}{1.5}=\dfrac{4}{15}\)

\(\Leftrightarrow x=\dfrac{11}{4}\cdot\dfrac{15}{4}=\dfrac{165}{16}\)

b: \(3\dfrac{1}{2}:\left(2x-3\right)=\dfrac{-3}{4}:0.2\)

\(\Leftrightarrow\dfrac{7}{2}:\left(2x-3\right)=\dfrac{-3}{4}:\dfrac{1}{5}=\dfrac{-15}{4}\)

\(\Leftrightarrow2x-3=\dfrac{7}{2}:\dfrac{-15}{4}=\dfrac{-7}{2}\cdot\dfrac{4}{15}=\dfrac{-28}{30}=\dfrac{-14}{15}\)

=>2x=-14/15+3=45/45-14/15=31/45

=>x=31/90

c: \(\dfrac{3x+2}{27}=\dfrac{3}{3x+2}\)

\(\Leftrightarrow\left(3x+2\right)^2=81\)

=>3x+2=9 hoặc 3x+2=-9

=>3x=7 hoặc 3x=-11

=>x=7/3 hoặc x=-11/3

d: \(\dfrac{5-x}{4}=\dfrac{2x+3}{2}\)

=>10-2x=8x+12

=>-10x=2

hay x=-1/5

28 tháng 9 2017

a) Vì |a|=\(\dfrac{3}{4}\)=>a=\(\dfrac{3}{4}\).Thay vào ta sẽ có:

A=3.\(\dfrac{3}{4}\)-4.\(\dfrac{3}{4}\).(\(\dfrac{-5}{6}\))+5.(\(\dfrac{-5}{6}\))

A=\(\dfrac{9}{4}-\left(\dfrac{-5}{2}\right)+\left(\dfrac{-25}{6}\right)\)

A=\(\dfrac{19}{4}\)-\(\dfrac{25}{6}\)

A=\(\dfrac{14}{24}\)=\(\dfrac{7}{12}\)

b, Thay vào, ta sẽ có:

A=3.\(\left(\dfrac{-2}{3}\right)-4.\left(\dfrac{-2}{3}\right).\dfrac{4}{5}+5.\dfrac{4}{5}\)

A=-2-\(\left(\dfrac{-32}{15}\right)\)+4

A=\(\dfrac{2}{15}\)+4

A=\(\dfrac{62}{15}\)

4 tháng 11 2017

5x2 - 7 = 38 => x2 = 9 => x = \(\pm\)3

Từ đây thay x vào \(\dfrac{3x-2}{4}\) để tìm y,z

12 tháng 10 2017

a)Ta có :

\(\dfrac{x}{2}=\dfrac{y}{5}=k\)

Mà x.y=3,6 => 2k+5k=3,6=>7k=3,6

Vậy k = \(\dfrac{18}{35}\)

\(x=2k\Rightarrow x=\dfrac{36}{35}\)

\(y=5k\Rightarrow y=\dfrac{18}{7}\)

12 tháng 10 2017

\(a,\dfrac{x}{2}=\dfrac{y}{5}\)

\(\rightarrow\)\(x.5=y.2\)

\(x.x.5=y.x.2\)

\(x^2.5=3,6.2\)

\(x^2.5=7,2\)

\(x^2=1,44\)

\(\rightarrow x=1,2\) hoặc \(x=-1,2\)

Ý b bạn làm tường tự nha

14 tháng 8 2018

a, Có \(\dfrac{3x-2y}{7}=\dfrac{4x+3y}{5}\)

=> 5(3x-2y)=7(4x+3y)

=> 15x-10y=28x+21y

=> 15x-28x=21y+10y

=> -13x=31y

=> \(\dfrac{x}{y}=\dfrac{31}{-13}=\dfrac{-31}{13}\)

b,\(\dfrac{5x-2y}{3x+4y}=\dfrac{-3}{4}\)

=> 4(5x-2y)=-3(3x+4y)

=> 20x-8y= -9x-12y

=> 20x+9x=-12y+8y

=> 29x=-4y

=> \(\dfrac{x}{y}=\dfrac{-4}{29}\)

7 tháng 10 2017

a.\(\left(3x-2\right)^2=16\)

Ta có: \(\left(3x-2\right)^2=16\)

\(\Rightarrow\left(3x-2\right)^2=\left(4\right)^2\)

\(\Rightarrow3x-2=4\)

\(\Rightarrow3x=6\)

\(\Rightarrow x=2\)

7 tháng 10 2017

b. \(\left(\dfrac{4}{5}x-\dfrac{3}{4}\right)^3=\dfrac{-8}{125}\)

\(\Rightarrow\left(\dfrac{4}{5}x-\dfrac{3}{4}\right)^3=\left(\dfrac{-2}{5}\right)^3\)

\(\Rightarrow\dfrac{4}{5}x-\dfrac{3}{4}=\dfrac{-2}{5}^{ }\)

\(\Rightarrow\dfrac{4}{5}x-=\dfrac{7}{20}\)

\(\Rightarrow x=\dfrac{7}{16}\)