1 . Cho \(\frac{2bz-3cy}{a}=\frac{3cx-az}{2b}=\frac{ay-2bx}{3c}\)
Chứng minh \(\frac{x}{a}=\frac{y}{2b}=\frac{z}{3c}\)
2 . Cho \(\frac{1}{c}=\frac{1}{2}\left(\frac{1}{a}+\frac{1}{b}\right)\left(\forall a,b,c\ne0;b\ne c\right)\). CMR : \(\frac{a}{b}=\frac{a-c}{c-b}\)