Ta có a:b:c:d=2:3:4:5
Suy ra: \(\frac{a}{2}\)=\(\frac{b}{3}\)=\(\frac{c}{4}\)=\(\frac{d}{5}\)và a+b+c+d=-42
\(\frac{a}{2}\)=\(\frac{b}{3}\)=\(\frac{c}{4}\)=\(\frac{d}{5}\)=\(\frac{a+b+c+d}{2+3+4+5}\)=\(\frac{-42}{14}\)= -3
Suy ra a=-6; b=-9;c=-12 và d=-15