Question

Cho x,y,z thỏa mãn \(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{z}{7}\) với x,y,z khác 0. Tính \(P=\dfrac{x-y+z}{x+2y-z}\)

Answer 1

Đặt \(x=2k;y=5k;z=7k\)

\(P=\dfrac{2k-5k+7k}{2k+10k-7k}=\dfrac{4k}{5k}=\dfrac{4}{5}\)