\[\frac{1}{(a - b)(a - c)} + \frac{1}{(b - a)(b - c)} - \frac{1}{(c - a)(b - c)} = 0\]
\[\frac{1^{\backslash b - c}}{(a - b)(a - c)} - \frac{1^{\backslash a - c}}{(a - b)(b - c)} + \frac{1^{\backslash a - b}}{(a - c)(b - c)} = 0\]
\[\frac{b - c - a + c + a - b}{(a - b)(a - c)(b - c)} = 0\ \ \]
\[0 = 0\]
\[ч.т.д.\]