\(tc1:\frac{a}{b}=\frac{c}{d}=>\frac{a}{b}=\frac{c}{d}=\frac{a+c}{b+d}\)
\(tc2:\frac{a}{b}=\frac{c}{d}=>\frac{a}{b}=\frac{c}{d}=\frac{a-c}{b-d}\)
\(tc3:\frac{a}{b}=\frac{c}{d}=\frac{e}{f}=>\frac{a}{b}=\frac{c}{d}=\frac{e}{f}=\frac{a+c+e}{b+d+f}\)
\(\frac{a}{b}=\frac{c}{d}=\frac{e}{f}=>\frac{a}{b}=\frac{c}{d}=\frac{e}{f}=\frac{a-c+e}{b-d+f}\)
chứng minh ak bạn