Question

Cho \(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}\)

\(A=\dfrac{x+y-z}{x-y+z};B=\dfrac{2x+3y+z}{x-2y-3z}\)

Answer 1

\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}=k\)

\(\Rightarrow x=2k;y=3k;z=4k\)

sau đó bạn tự thay vào A và B r tính nhá

Answer 2

Đặt:

\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}=k\)

\(\Rightarrow\left\{{}\begin{matrix}x=2k\\y=3k\\z=4k\end{matrix}\right.\)

\(\Rightarrow A=\dfrac{2k+3k-4k}{2k-3k+4k}=\dfrac{k}{3k}=\dfrac{1}{3}\)

\(\Rightarrow B=\dfrac{2.2k+3.3k+4k}{2k-2.3k-3.4k}=\dfrac{4k+9k+4k}{2k-6k-12k}=\dfrac{17k}{-16k}=\dfrac{17}{-16}\)