Question

[khai thanh Tang]

\(\frac{X-1}{2}=\frac{Y-2}{3}=\frac{Z-3}{4}\)

VÀ 2x+3y-z=50

giúp mình với, mình đang cần gấp, Cám ơn

Answer 1

[vo tran hien]

\(\frac{x-1}{2}=\frac{y-2}{3}\Rightarrow\frac{3\left(x-1\right)}{2}=y-2\Rightarrow y=\frac{3\left(x-1\right)}{2}+2=\frac{3\left(x-1\right)+4}{2}\)(1)

\(\frac{x-1}{2}=\frac{z-3}{4}\Rightarrow\frac{4\left(x-1\right)}{2}=z-3\Rightarrow z=\frac{4\left(x-1\right)}{2}+3=\frac{4\left(x-1\right)+6}{2}\)(2)

Từ (1) và (2) => 2x+3y-z=\(2x+3\left(\frac{3\left(x-1\right)+4}{2}\right)-\frac{4\left(x-1\right)+6}{2}=50\)

\(\Rightarrow\frac{4x}{2}+\frac{9\left(x-1\right)+12}{2}-\frac{4\left(x-1\right)+6}{2}=50\)

\(\Rightarrow\frac{4x+9x-9+12-4x+4-6}{2}=50\)

\(\Rightarrow9x+1=100\)

\(\Rightarrow9x=99\)

\(\Rightarrow x=11\)

Vì \(y=\frac{3\left(x-1\right)+4}{2}=\frac{3\left(11-1\right)+4}{2}=\frac{34}{2}=17\Leftrightarrow y=17\)

Vì \(z=\frac{4\left(x-1\right)+6}{2}=\frac{4\left(11-1\right)+6}{2}+\frac{46}{2}=23\Leftrightarrow z=23\)

Vậy   x=11

         y=17

         z=23

Answer 2

[Phuong Nguyen]

\(\Rightarrow\frac{2\left(x-1\right)}{2.2}=\frac{3\left(y-2\right)}{3.3}=\frac{z-3}{4}\) 

\(\Rightarrow\frac{2x-2}{4}=\frac{3y-6}{9}=\frac{z-3}{4}\) 

Áp dụng t/c dãy tỉ số = nhau

\(\Rightarrow\frac{2x-2}{4}=\frac{3y-6}{9}=\frac{z-3}{4}=\frac{2x-2+3y-6-z+3}{4+9-4}=\frac{50-2-6+3}{9}=\frac{45}{9}=5\) 

\(\Rightarrow\hept{\begin{cases}\frac{x-1}{2}=5\Rightarrow x-1=10\Rightarrow x=11\\\frac{y-2}{3}=5\Rightarrow y-2=15\Rightarrow y=17\\\frac{z-3}{4}=5\Rightarrow z-3=20\Rightarrow z=23\end{cases}}\)