

Cho [tex]\frac{a}{b+c}=\frac{b}{a+c}=\frac{c}{a+b}[/tex] .
Tính : [tex]M = \frac{abc}{\left ( a+b \right )\left ( b+c \right )\left ( a+c \right )}[/tex]
Tính : [tex]M = \frac{abc}{\left ( a+b \right )\left ( b+c \right )\left ( a+c \right )}[/tex]