Спростити вираз. СРОЧНО!!!!

[tex] \frac{2ab - {a}^{2} - {b}^{2} + {c}^{2} }{ {a}^{2} + {c}^{2} - {b}^{2} + 2ac} = \frac{ - ( {a}^{2} - 2ab + {b}^{2}) + {c}^{2} }{( {a}^{2} + 2ac + {c}^{2} ) - {b }^{2} } = \frac{ {c}^{2} - (a - b) {}^{2} }{(a + c) {}^{2} - {b}^{2} } = \\ = \frac{(c + a - b)(c - a + b)}{(a + c + b)(a + c - b)} = \frac{c - a + b}{a + c + b} [/tex]