a2=bc=>a.a=bc=>\(\frac{a}{b}=\frac{c}{a}\)
Đặt \(\frac{a}{b}=\frac{c}{a}=k\Rightarrow a=bk;c=ak\)
=>\(\frac{a+b}{a-b}=\frac{bk+b}{bk-b}=\frac{b\left(k+1\right)}{b\left(k-1\right)}=\frac{k+1}{k-1}\)
\(\frac{c+a}{c-a}=\frac{ak+a}{ak-a}=\frac{a\left(k+1\right)}{a\left(k-1\right)}=\frac{k+1}{k-1}\)
Vậy với a2=bc thì \(\frac{a+b}{a-b}=\frac{c+a}{c-a}\left(=\frac{k+1}{k-1}\right)\)