Question

2) Решите систему уравнений

Answer 1

$left { {{y+2x=5} atop {2x-xy=-1}} right.\\left { {{y=5-2x} atop {2x-x(5-2x)=-1}} right.\\left { {{y=5-2x} atop {2x-5x+2x^{2}+1=0 }} right.\\left { {{y=5-2x} atop {2x^{2}-3x+1=0 }} right.\\2x^{2} -3x+1=0\\D=(-3)^{2}-4*2*1=9-8=1\\x_{1}=frac{3+1}{4}=1\\x_{2}=frac{3-1}{4}=frac{1}{2}=0,5\\y_{1} =5-2x=5-2*1=3\\y_{2}=5-2*0,5=4$

Ответ : (1 ; 3) , ( 0,5 ; 4)