Vì \(\dfrac{x}{y}=\dfrac{7}{3}\Rightarrow\dfrac{x}{7}=\dfrac{y}{3}\Rightarrow\dfrac{5x}{35}=\dfrac{2y}{6}\)

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\dfrac{5x}{35}=\dfrac{2y}{6}=\dfrac{5x-2y}{35-6}=\dfrac{87}{29}=3\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{5x}{35}=3\Rightarrow\dfrac{x}{7}=3\Rightarrow x=21\\\dfrac{2y}{6}=3\Rightarrow\dfrac{y}{3}=3\Rightarrow y=9\end{matrix}\right.\)

Vậy ..................

Chúc bạn học tốt!

Chọn đáp án B.

\(\dfrac{3x-2y}{5}\)=\(\dfrac{2z-5x}{3}\)=\(\dfrac{5y-3z}{2}\)

⇒\(\dfrac{15x-10y}{25}\)=\(\dfrac{6z-15x}{9}\)=\(\dfrac{10y-6z}{4}\)

Áp dụng tính chất dãy tỉ số bằng nhau:

\(\dfrac{15x-10y}{25}\)=\(\dfrac{6z-15x}{9}\)=\(\dfrac{10y-6z}{4}\)=\(\dfrac{15x-10y+6z-15x+10y-6z}{25+9+4}\)=0

⇒3x-2y=2z-5x=5y-3z=0

* 3x-2y=0⇒3x=2y⇒\(\dfrac{x}{2}\)=\(\dfrac{y}{3}\) 

* 2z-5x=0⇒2z=5x⇒\(\dfrac{z}{5}\)=\(\dfrac{x}{2}\) 

Áp dụng tính chất dãy tỉ số bằng nhau:

\(\dfrac{x}{2}\)=\(\dfrac{y}{3}\)=\(\dfrac{z}{5}\)=\(\dfrac{x+y+z}{2+3+5}\)=\(\dfrac{-50}{10}\)=-5

\(\dfrac{x}{2}\)=-5⇒x=-10

\(\dfrac{y}{3}\)=-5⇒y=-15

\(\dfrac{z}{5}\)=-5⇒z=-25

Vậy x=-10;y=-15;z=-25

x/y=7/3 =>x/7=y/3 = 5x/35 = 2y/6 = 5x-2y/35-6 = 3

Vậy x/7=3           ;            y/3=3

         x=21                         y=9

Ta co: x/y=7/3=>x/7=y/3

Ap dung tinh chat cua day ti so bang nhau, ta co:

x/7=y/3=5x/35=2y/6=5x-2y/35-6=87/29=3

Do do: x/7=3=>x=3*7=21

          y/3=3=>y=3*3=9

a: Áp dụng tính chất của dãy tỉ số bằng nhau, ta được:

\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{5}=\dfrac{x-2y+3z}{2-2\cdot3+3\cdot5}=\dfrac{33}{11}=3\)

Do đó: x=6; y=9; z=15

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\frac{x}{y}=\frac{7}{3}\Rightarrow\frac{x}{3}=\frac{y}{7}=\frac{5x}{15}=\frac{2y}{14}=\frac{5x-2y}{15-14}=\frac{87}{1}=87\)

vậy x/3=87 => x=87.3=261

      y/7=87 => y=87.7=609

\(2x=3y\text{⇒}\dfrac{x}{3}=\dfrac{y}{2}\text{⇒}\dfrac{x}{21}=\dfrac{y}{14}\)

\(5y=7z\text{⇒}\dfrac{y}{7}=\dfrac{z}{5}\text{⇒}\dfrac{y}{14}=\dfrac{z}{10}\)

⇒\(\dfrac{x}{21}=\dfrac{y}{14}=\dfrac{z}{10}\)⇒\(\dfrac{3x}{63}=\dfrac{7y}{98}=\dfrac{5z}{50}\)

Áp dụng tính chất dãy tỉ số bằng nhau, ta có:

\(\dfrac{3x}{63}=\dfrac{7y}{98}=\dfrac{5z}{50}=\dfrac{3x-7y+5z}{63-98+50}=\dfrac{30}{15}=2\)

⇒x=42,y=28,z=20

\(\dfrac{x}{3}=\dfrac{y}{2}\)⇒\(\dfrac{x}{15}=\dfrac{y}{10}\)

\(\dfrac{x}{5}=\dfrac{z}{7}\text{⇒}\dfrac{x}{15}=\dfrac{z}{21}\)

⇒\(\dfrac{x}{15}=\dfrac{y}{10}=\dfrac{z}{21}\)⇒\(\dfrac{x}{15}=\dfrac{2y}{20}\)

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\dfrac{x}{15}=\dfrac{2y}{20}=\dfrac{x+2y}{15+20}=\dfrac{-112}{35}=\dfrac{-16}{5}\)

⇒x=48,y=32,z=336/5

\(\dfrac{x}{y}=\dfrac{3}{7}.\\ \Rightarrow x=\dfrac{3}{7}y.\\ x-y=16.\\\Rightarrow\dfrac{3}{7}y-y=16.\\ \Rightarrow y=-28.\\ \Rightarrow x=-12.\)

\(\dfrac{x}{1,8}=\dfrac{y}{3,2}.\\ \Rightarrow\dfrac{x}{y}=\dfrac{1,8}{3,2}=\dfrac{9}{16}.\\ \Rightarrow x=\dfrac{9}{16}y.\\ y-x=7.\\ \Rightarrow y-\dfrac{9}{16}y=7.\\ \Leftrightarrow y=16.\\ \Leftrightarrow x=9.\)

\(\dfrac{x}{5}=\dfrac{y}{8}.\\ \Rightarrow\dfrac{x}{y}=\dfrac{5}{8}.\\ \Rightarrow x=\dfrac{5}{8}y.\\ x+2y=42.\\ \Rightarrow\dfrac{5}{8}y+2y=42.\\ \Leftrightarrow y=16.\\ \Rightarrow x=10.\)

\(\dfrac{x}{5}=\dfrac{y}{7}.\\ \Rightarrow\dfrac{x}{y}=\dfrac{5}{7}.\\ \Rightarrow x=\dfrac{5}{7}y.\\ x.y=35.\\ \Rightarrow\dfrac{5}{7}y.y=35.\\ \Leftrightarrow y^2=49.\\ \Leftrightarrow u=\pm7.\\ \Rightarrow x=\pm5.\)

Câu hỏi từ thuở nào rồi má :)))

7) vì \(\dfrac{x}{5}\)=\(\dfrac{y}{6}\)=\(\dfrac{z}{7}\)và x-y+z=36

Nên theo tính chất của dãy tỉ số bằng nhau ta có:

 \(\dfrac{x}{5}\)=\(\dfrac{y}{6}\)=\(\dfrac{z}{7}\)=\(\dfrac{x-y+z}{5-6+7}\)=\(\dfrac{36}{6}\)=6

 \(\Rightarrow\)x=6.5=30

     y=6.6=36

     z=6.7=42

vậy x=30,y=36,z=42