-xx=-2x4

-xx=-8

xx=8

x²=8

x= căn bâc của 8

a; \(\dfrac{-x}{4}\) = \(\dfrac{-2}{x}\)

    -\(x.x\) = -2.4

    -\(x^2\) = -8

      \(x^2\) = 8

      \(\left[{}\begin{matrix}x=-\sqrt{8}\\x=\sqrt{8}\end{matrix}\right.\)

Vậy \(x\in\) {-\(\sqrt{8}\); \(\sqrt{8}\)}

b; \(\dfrac{-4}{8}\) = \(\dfrac{x}{-10}\) = \(\dfrac{-7}{y}\) = \(\dfrac{7}{21}\)

     \(-\dfrac{4}{8}\) = - \(\dfrac{1}{2}\) ≠  \(\dfrac{1}{3}\) = \(\dfrac{7}{21}\)

Vậy pt vô nghiệm

Mấy bài còn lại tương tự nhé cậu

Đây đâu phải toán lớp một mà là toán lớp 6 thì có

a./ \(\frac{x}{5}=\frac{y}{7}=\frac{z}{4}=\frac{x-y+z}{5-7+4}=\frac{-10}{2}=-5\)

\(\Rightarrow x=-25;y=-35;z=-20\)

b./ \(\frac{x}{5}=\frac{y}{-4}=\frac{z}{-7}=\frac{x+y-z}{5-4-\left(-7\right)}=\frac{-40}{6}=-5\)

\(\Rightarrow x=-25;y=20;z=35\)

1, ta co \(\frac{x}{5}=\frac{y}{6}=\frac{x}{20}=\frac{y}{24}\)

\(\frac{y}{8}=\frac{z}{7}=\frac{y}{24}=\frac{z}{21}\)

=>\(\frac{x}{20}=\frac{y}{24}=\frac{z}{21}=\frac{x+y-z}{20+24-21}=\frac{69}{23}=3\)

=>\(x=3\cdot20=60\)

    \(y=3\cdot24=72\)

    \(z=3\cdot21=63\)

3. ta co \(\frac{x}{15}=\frac{y}{7}=\frac{z}{3}=\frac{t}{1}=\frac{x+y-z+t}{15-7+3-1}=\frac{10}{10}=1\)

=> \(x=1\cdot15=15\)

     \(y=1\cdot7=7\)

     \(z=1\cdot3=3\)

     \(t=1\cdot1=1\)

Áp dụng tính chất dãy tỉ số bằng nhau

\(\frac{x}{5}=\frac{y}{7}=\frac{z}{9}=\frac{x-y+z}{5-7+9}=\frac{315}{7}=45\)

  suy ra:   x/5 = 45   =>  x  =  225

               y/7 = 45  =>  y  =  315

               z/9 = 45  =>  z  =  405

a/ \(\frac{2}{3}+\frac{4}{35}< \frac{x}{105}< \frac{1}{7}+\frac{2}{5}+\frac{1}{3}\)

\(\Rightarrow\frac{82}{105}< \frac{x}{105}< \frac{92}{105}\)

\(\Rightarrow82< x< 92\)

\(\Rightarrow x=\left\{83;84;85;86;87;88;89;90;91\right\}\)

b/ \(-\frac{7}{15}+\frac{8}{60}+\frac{24}{90}\le\frac{x}{15}\le\frac{3}{5}+\frac{8}{30}+-\frac{4}{10}\)

\(\Rightarrow-\frac{1}{15}\le\frac{x}{15}\le\frac{7}{15}\)

\(\Rightarrow-1\le x\le7\)

\(\Rightarrow x=\left\{-1;0;1;2;3;4;5;6;7\right\}\)

-4/8=-12/24=z/24. Suy ra z=-12

-4/8=-1/2=5/-10=x/-10. Suy ra x=5

-4/8=-1/2=-7/14=-7/y. Suy ra y=14

Ủng hộ mk nha

-4/8=-12/24=z/24. Suy ra z=-12

-4/8=-1/2=5/-10=x/-10. Suy ra x=5

-4/8=-1/2=-7/14=-7/y. Suy ra y=14

Ủng hộ mk nha, mãi chưa đc nào cả !!

\(\frac{-4}{8}=\frac{x}{-10}\Leftrightarrow\left(-4\right).\left(-10\right)=8.x\Rightarrow x=\frac{\left(-4\right).\left(-10\right)}{8}=\frac{40}{8}=5\)

\(\frac{5}{-10}=\frac{-7}{y}\Leftrightarrow5.y=\left(-10\right)\left(-7\right)\Rightarrow y=\frac{\left(-10\right).\left(-7\right)}{5}=\frac{70}{5}=14\)

\(\frac{-7}{14}=\frac{z}{-24}\Leftrightarrow\left(-7\right).\left(-24\right)=14.z\Rightarrow z=\frac{\left(-7\right).\left(-24\right)}{14}=\frac{168}{14}=12\)

Vậy x = 5 ; y = 14 ; z = 12

a)\(2x=3y,4y=5z\Leftrightarrow\frac{x}{3}=\frac{y}{2},\frac{y}{5}=\frac{z}{4}\Leftrightarrow\frac{x}{15}=\frac{y}{10},\frac{y}{10}=\frac{z}{8}\)

\(\Rightarrow\frac{x}{15}=\frac{y}{10}=\frac{z}{8}\Leftrightarrow\frac{2x}{30}=\frac{y}{10}=\frac{2z}{16}\)

ADTCDTS=NHAU TA CÓ

\(\frac{2x}{30}=\frac{y}{10}=\frac{2z}{16}=\frac{2x+y-2z}{30+10-16}=\frac{24}{24}=1\)

x=15

y=10

z=8

b) Ta có BCNN(2,3,4)=12

\(\Rightarrow\frac{2x}{12}=\frac{3x}{12}=\frac{4z}{12}\Leftrightarrow\frac{x}{6}=\frac{y}{4}=\frac{z}{3}\)

\(\Rightarrow\frac{x}{6}=\frac{y}{4}=\frac{z}{3}\Leftrightarrow\frac{x^2}{36}=\frac{y^2}{16}=\frac{z^2}{9}\)

ADTCDTS=NHAU TA CÓ

\(\frac{x^2}{36}=\frac{y^2}{16}=\frac{z^2}{9}=\frac{x^2+y^2+z^2}{36+16+9}=\frac{61}{61}=1\)

\(\frac{x^2}{36}=1\Rightarrow x^2=36\Rightarrow x=+_-6\)

\(\frac{y^2}{16}=1\Rightarrow x=+_-4\)

\(\frac{z^2}{9}=1\Rightarrow z=+_-3\)

TUỰ KẾT LUẬN NHA BẠN

C)\(\frac{x-6}{3}=\frac{y-8}{4}=\frac{z-10}{5}\Leftrightarrow\frac{x^2-36}{9}=\frac{y^2-64}{16}=\frac{z^2-100}{25}\)

ADTCDTS=NHAU TA CÓ

\(\frac{x^2-36}{9}=\frac{y^2-64}{16}=\frac{z^2-100}{25}=\frac{\left(x^2-36\right)+\left(y^2-64\right)+\left(z^2-100\right)}{9+16+25}\)

\(=\frac{x^2-36+y^2-64+z^2-100}{50}=\frac{\left(x^2+y^2+z^2\right)-\left(36-64-100\right)}{50}\)

\(=\frac{\left(x^2+y^2+z^2\right)-\left(36+64+100\right)}{50}=\frac{200-200}{50}=\frac{0}{50}=0\)

\(\Rightarrow\frac{x^2-36}{9}=0\Rightarrow x^2-36=0\Rightarrow x^2=36\Rightarrow x=+_-6\)

\(\frac{y^2-64}{16}=0\Rightarrow y^2-64=0\Rightarrow y^2=64\Rightarrow y==+_-8\)

\(\frac{z^2-100}{25}=0\Rightarrow z^2-100=0\Rightarrow z^2=100\Rightarrow z=+_-10\)

TỰ KẾT LUẠN NHA

1) 

a) \(-\frac{8}{15}< \frac{x}{45}< -\frac{2}{5}\)

Lại có: \(-\frac{8}{15}=\frac{-24}{45};-\frac{2}{5}=\frac{-18}{45}\)

=> \(-\frac{24}{45}< \frac{x}{45}< -\frac{18}{45}\)

=> -24 < x < - 18 

=> x \(\in\){ - 23; -22; -21; -20 ; -19 } ( thử lại thỏa mãn )

b) \(x=\frac{-4}{3}+\frac{-7}{5}=-\frac{4.5}{3.5}+\frac{-7.3}{5.3}=-\frac{41}{15}\)

c) \(\frac{83}{x}=\frac{13}{4}+\frac{9}{10}=\frac{83}{20}\)

=> x = 20 ( thử lại thỏa mãn) 

d) \(x=\frac{10}{8}+\frac{-24}{48}+\frac{105}{-120}=-\frac{1}{8}\)

e) \(\left|x-\frac{1}{2}\right|=\left|-\frac{2}{7}\right|+\frac{5}{4}\)

\(\left|x-\frac{1}{2}\right|=\frac{2}{7}+\frac{5}{4}\)

\(\left|x-\frac{1}{2}\right|=\frac{43}{28}\)

TH1: \(x-\frac{1}{2}=\frac{43}{28}\)

         \(x=\frac{57}{28}\)

TH2: \(x-\frac{1}{2}=-\frac{43}{28}\)

      \(x=-\frac{29}{28}\)