AE vô giúp với! Cần gấp!!!

T

toxic123

N

nerversaynever

1/
[TEX]\begin{array}{l}x = - \frac{{by + cz}}{a}\\xy + yz + xz = - \frac{{by + cz}}{a}\left( {y + z} \right) + yz = \frac{1}{a}\left( { - b{y^2} - \left( {b + c - a} \right)zy - c{z^2}} \right) = \frac{{f\left( y \right)}}{a}\\{\Delta _f} = {\left( {b + c - a} \right)^2} - 4bc = {a^2} + {b^2} + {c^2} - 2ab - 2bc - 2ac \le 0\end{array}[/TEX]
->đpcm
2/
[TEX]\begin{array}{l}kabc = ab + bc + ca + a + b + c \le ab + b\left( {a - 2} \right) + ac + a + b + b - 1 = 2ab + ac + a - 1 < 2ab + ac + a\\ \to kbc < 2b + c + 1 \to kbc \le 3b - 1 \to kc < 3\\gt \to kc > 1 \Rightarrow kc = 2\end{array}[/TEX]
[TEX]\begin{array}{l}k = 1;c = 2 \to \left( {a - 3} \right)\left( {b - 3} \right) = 11 \Rightarrow a = 14;b = 4\\k = 2;c = 1 \to \left( {a - 2} \right)\left( {b - 2} \right) = 5 \Rightarrow a = 7;b = 3\end{array}[/TEX]
(a,b,c,k)=(14;4;2;1);(7;3;1;2)
 
You must log in or register to reply here.
Top Bottom