引用:
原帖由 shmilyho 於 2024-12-23 16:58 發表 
這個行列式要如何證明?謝謝。
吸收一樓老師的提示
\(\left|\ \matrix{a^2&ab&b^2\cr b^2&bc&c^2 \cr c^2&ca&a^2} \right|\ \matrix{÷ a^2 \cr÷ b^2\cr÷ c^2}\)
\(=\left|\ \matrix{\displaystyle 1&\frac{b}{a}&\left(\frac{b}{a}\right)^2\cr 1&\frac{c}{b}&\left(\frac{c}{b}\right)^2 \cr 1&\frac{a}{c}&\left(\frac{a}{c}\right)^2} \right| a^2b^2c^2\)
\(\displaystyle =\left(\frac{b}{a}-\frac{c}{b}\right)\left(\frac{c}{b}-\frac{a}{c}\right)\left(\frac{a}{c}-\frac{b}{a}\right)a^2b^2c^2\)
\(\displaystyle =\left[\left(\frac{b}{a}-\frac{c}{b}\right)(ab)\right]
\left[\left(\frac{c}{b}-\frac{a}{c}\right)(bc)\right]
\left[\left(\frac{a}{c}-\frac{b}{a}\right)(ac)\right]\)
\(=(b^2-ac)(c^2-ab)(a^2-bc)\)