\(\Delta =\begin{vmatrix} a&b&c\\b&c&a\\c&a&b\end{vmatrix}\)
⇒ \(\Delta =\begin{vmatrix} {a +b+c}&b&c\\{a +b+c}&c&a\\{a +b+c}&a&b\end{vmatrix}\)
(संक्रिया C1 → C1 + C2 + C3 से)
⇒ \(\Delta =(a + b+c)\begin{vmatrix} 1&b&c\\1&c&a\\1&a&b\end{vmatrix}\)
[C1 से (a + b + c) उभयनिष्ठ लेने पर।
⇒ \(\Delta =(a + b+c)\begin{vmatrix} 1&b&c\\1&c-b&a-c\\1&a-b&b-c\end{vmatrix}\)
(संक्रियाओं R2 → R2 - R1 और R3 → R3 - R1 से)
⇒ \(\Delta =(a + b+c)\begin{vmatrix} c-b&a-c\\a-b&b-c\end{vmatrix}\)
(R1 के सापेक्ष प्रयास करने पर)
⇒ \(\Delta =(a + b+c) \{-(c - b)^2 - (a- b)(a -c)\}\)
⇒ \(\Delta =(a + b+c) (-a^2 - b^2 - c^2 + ab + bc + ca)\)
⇒ \(\Delta =-\frac 12(a + b+c) (2a^2+ 2b^2 +2c^2 -2 ab -2bc -2ca)\)
⇒ \(\Delta =-\frac 12(a + b+c) \{(a - b)^2 + (b - c^2) + (c -a)^2\}\)
⇒ \(\Delta < 0\)
\([\because a + b + c >0, (a - b)^2 >0, (b-c)^2 >0, (c - a)^2 >0]\)