| a2−bc |
| (a+b)(a+c) |
| a2+ac−ac−bc |
| (a+b)(a+c) |
| a(a+c)−c(a+b) |
| (a+b)(a+c) |
| a |
| a+b |
| c |
| a+c |
∴
| b2−ca |
| (b+c)(b+a) |
| b |
| b+c |
| a |
| b+a |
| c2−ab |
| (c+a)(c+b) |
| c |
| c+a |
| b |
| b+c |
∴左-右=
| a2−bc |
| (a+b)(a+c) |
| b2−ca |
| (b+c)(b+a) |
| c2−ab |
| (c+a)(c+b) |
| a |
| a+b |
| c |
| a+c |
| b |
| b+c |
| a |
| b+a |
| c |
| c+a |
| b |
| b+c |
∴等式成立．
| a2−bc |
| (a+b)(a+c) |
| b2−ca |
| (b+c)(b+a) |
| ab−c2 |
| (c+a)(c+b) |
| a2−bc |
| (a+b)(a+c) |
| a2+ac−ac−bc |
| (a+b)(a+c) |
| a(a+c)−c(a+b) |
| (a+b)(a+c) |
| a |
| a+b |
| c |
| a+c |
| b2−ca |
| (b+c)(b+a) |
| b |
| b+c |
| a |
| b+a |
| c2−ab |
| (c+a)(c+b) |
| c |
| c+a |
| b |
| b+c |
| a2−bc |
| (a+b)(a+c) |
| b2−ca |
| (b+c)(b+a) |
| c2−ab |
| (c+a)(c+b) |
| a |
| a+b |
| c |
| a+c |
| b |
| b+c |
| a |
| b+a |
| c |
| c+a |
| b |
| b+c |