Question

Giúp mik với các bro ới;-;

Answer 1

Đặt \(\dfrac{x}{-4}=\dfrac{y}{-7}=\dfrac{z}{3}=k\)

=>x=-4k; y=-7k; z=3k

\(A=\dfrac{-2x+y+5z}{2x-3y-6z}=\dfrac{8k-7k+15k}{-8k+21k-18k}=-\dfrac{16}{5}\)

Answer 2

Áp dụng tc dtsbn:

\(\dfrac{x}{-4}=\dfrac{y}{-7}=\dfrac{z}{3}=\dfrac{-2x+y+5z}{8-7+15}=\dfrac{2x-3y-6z}{-8+21-18}\\ \Rightarrow A=\dfrac{8-7+15}{-8+21-18}=\dfrac{16}{-5}=-\dfrac{16}{5}\)