Question

Решить систему уравнений: х-у=-5 х²-2ху-у²=17

Answer 1

$\left \{ {{x-y=-5} \atop {x^2-2xy-y^2=17}} \right. \\\\(x-y)^2=x^2-2xy+y^2\; \; \to \\\\ x^2-2xy-y^2=(x^2-2xy+y^2)-2y^2=(x-y)^2-2y^2=\\\\=(-5)^2-2y^2=25-2y^2\\\\ \left \{ {{x-y=-5} \atop {25-2y^2=17}} \right. \; \left \{ {{x-y=-5} \atop {2y^2=8}} \right. \; \left \{ {{x=y-5} \atop {y=\pm 2}} \right. \\\\ \left \{ {{x=2-5=-3} \atop {y=2}} \right.\; \; ili\; \; \left \{ {{x=-2-5=-7} \atop {y=-2}} \right. \\\\Otvet:\; \; (-3,2)\; ,\; (-7,-2).$