1 câu trả lời
\(\begin{array}{l} a\left( {a + b - c} \right) + b\left( {a + b - c} \right) - c\left( {a + b - c} \right) = 12 + 15 - 8\\ \Leftrightarrow \left( {a + b - c} \right)\left( {a + b - c} \right) = 19\\ \Leftrightarrow {\left( {a + b - c} \right)^2} = 19\\ \Rightarrow \left[ \begin{array}{l} a + b - c = \sqrt {19} \\ a + b - c = - \sqrt {19} \end{array} \right.\\ + )\,a + b - c = \sqrt {19} \Rightarrow a = \frac{{12}}{{\sqrt {19} }};b = \frac{{15}}{{\sqrt {19} }};c = \frac{8}{{\sqrt {19} }}\\ + )a + b - c = - \sqrt {19} \Rightarrow a = - \frac{{12}}{{\sqrt {19} }};b = - \frac{{15}}{{\sqrt {19} }};c = - \frac{8}{{\sqrt {19} }} \end{array}\)
