Question

Cho \(\dfrac{a}{c}\)=\(\dfrac{b}{d}\)(giả thiết các tỉ số đều có nghĩa)

Answer 1

\(\dfrac{a}{c}=\dfrac{b}{d}=\dfrac{a+b}{c+d}\Rightarrow\dfrac{a^2}{c^2}=\dfrac{\left(a+b\right)^2}{\left(c+d\right)^2}\left(1\right)\)

\(\dfrac{a}{c}=\dfrac{b}{d}\Rightarrow\dfrac{a^2}{c^2}=\dfrac{b^2}{d^2}=\dfrac{a^2+b^2}{c^2+d^2}\left(2\right)\)

\(\left(1\right),\left(2\right)\Rightarrowđpcm\)