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).