Xét \(\dfrac{a}{b}=\dfrac{b}{c}=\dfrac{c}{a}=\dfrac{a+b+c}{b+c+a}=1\)
\(\Rightarrow\)\(\dfrac{a}{b}=\dfrac{b}{c}=\dfrac{c}{a}=1\)
\(\Rightarrow a=b=c\)
Ta có:
\(\dfrac{a}{b}=\dfrac{b}{c}=\dfrac{c}{a}\)
\(=\dfrac{a+b+c}{b+c+a}=1\)
\(\Rightarrow\dfrac{a}{b}=1\Rightarrow a=b\) ( 1 )
\(\dfrac{b}{c}=1\Rightarrow b=c\) ( 2 )
\(\dfrac{c}{a}=1\Rightarrow c=a\) ( 3 )
Từ ( 1 ) ; ( 2 ) ; ( 3 ) => a = b = c.
\(\dfrac{a}{b}=\dfrac{b}{c}=\dfrac{c}{a}\)
- Áp dụng tính chất của dãy tỉ số bằng nhau, ta có:
\(\dfrac{a}{b}=\dfrac{b}{c}=\dfrac{c}{a}=\dfrac{a+b+c}{b+c+a}=1\)
=> A=B=C