Bài làm
Ta có: 3/x = 21/35y = y/25 = -18/z = 1/15
=> z = -18 . 15 : 1 = -270
=> y = 25 . ( -18 ) : z = 25 . ( -18 ) : ( -270 ) = 5/3
=> x = 3 . 35y : 21 = 3 . 35 . 5/3 : 21 = 25/3
Vậy x = 25/3, y = 5/3, z = -270
\(\frac{3}{x}=\frac{21}{35y}=\frac{y}{25}=-\frac{18}{z}=\frac{1}{15}\)
Xét : \(\frac{3}{x}=\frac{1}{15}\Leftrightarrow45=x\Leftrightarrow x=45\)
Xét : \(\frac{y}{25}=\frac{1}{15}\Leftrightarrow15y=25\Leftrightarrow y=\frac{5}{3}\)
Xét : \(-\frac{18}{z}=\frac{1}{15}\Leftrightarrow-270=x\Leftrightarrow x=-270\)
