Question

Cho\(\frac{x}{3}=\frac{y}{4};\frac{y}{5}=\frac{z}{6}\).Tính \(M=\frac{2x+3y+4z}{3x+4y+5z}\)

Answer 1

\(\frac{x}{3}=\frac{y}{4}\Rightarrow\frac{x}{15}=\frac{y}{20}\left(1\right)\)

\(\frac{y}{5}=\frac{z}{6}\Rightarrow\frac{y}{20}=\frac{z}{24}\left(2\right)\)

từ (1) và (2) => \(\frac{x}{15}=\frac{y}{20}=\frac{z}{24}\)

đặt \(\frac{x}{15}=\frac{y}{20}=\frac{z}{24}=k\Rightarrow x=15k,y=20k,z=24k\)

thay x=15k, y=20k, z=24k vào M ta có:

\(M=\frac{2.15k+3.20k+4.24k}{3.15k+4.20k+5.24k}=\frac{30k+60k+96k}{45k+80k+120k}=\frac{186k}{245k}=\frac{186}{245}\)

vậy M=\(\frac{186}{245}\)