Question

Решить систему уравнений:

4xy - y = -40
5x - 4xy = 27

Answer 1

$\left \{ {{4xy-y=-40,} \atop {5x-4xy=27;}} \right. \left \{ {{5x-y=-13,} \atop {5x-4xy=27;}} \right. \left \{ {{y=13+5x,} \atop {5x-4x*(13+5x)=27;}} \right. \left \{ {{y=13+5x,} \atop {-47x-20x^2=27;}} \right. \\ \\ 20x^2+47x+27=0 \\ \\ D=2209-2160=49 \\ \\ \sqrt{D}=7 \\ \\ x_{1}=\frac{-47-7}{40}=-1,35 \\ \\ x_{2}=-1 \\ \\ \left \{ {{ x_{1}=-1,35,} \atop {y_{1}=6,25;}} \right. \left \{ {{x_{2}=-1,} \atop {y_{2}=8;}} \right.$
Ответ:(-1,35;6,25);(-1;8).