Question

Решить систему уравнений. система y^2+xy=4 x^2+xy=-3 решите

Answer 1

Сначала из 1 уравнения вычтем 2-ое. А затем сложим два уравнения.

$\left \{ {{y^2+xy=4} \atop {x^2+xy=-3}} \right. \; \left \{ {{y^2-x^2=7} \atop {x^2+2xy+y^2=1}} \right. \; \left \{ {{(y-x)(y+x)=7} \atop {(x+y)^2=1}} \right. \; \left \{ {{(y-x)\cdot 1=7\; ili\; (x-y)\cdot (-1)=7} \atop {x+y=1\; ili\; x+y=-1}} \right. \\\\a)\; \left \{ {{y-x=7} \atop {x+y=1}} \right. \; \left \{ {{2y=8} \atop {2x=-6}} \right. \; \left \{ {{y=4} \atop {x=-3}} \right. \\\\b)\; \left \{ {{-(x-y)=7} \atop {x+y=-1}} \right. \; \left \{ {{y-x=7} \atop {x+y=-1}} \right.$

$\left \{ {{2y=6} \atop {2x=-8}} \right. \; \left \{ {{y=3} \atop {x=-4}} \right. \\\\Otvet:\; \; (-3,4),\; (-4,3).$