\(b^2=ac\Rightarrow\frac{a}{b}=\frac{b}{c}\Rightarrow\frac{a}{b}=\frac{2007b}{2007c}=\frac{a+2007b}{b+2007c}\)
\(\Rightarrow\frac{\left(a+2007b\right)^2}{\left(b+2007c\right)^2}=\frac{a^2}{b^2}=\frac{a}{b}\cdot\frac{a}{b}=\frac{a}{b}\cdot\frac{b}{c}=\frac{a}{c}\) (đpcm)