Question

решите систему уравнений

x^2+2y^2=4
x-y=4

Answer 1

$\left \{ {{x^{2}+2y^{2} =4 } \atop {x-y=4}} \right.\\\\\left \{ {{x=y+4} \atop {(y+4)^{2}+2y^{2}=4  }} \right.\\\\\left \{ {{x=y+4} \atop {y^{2}+8y+16+2y^{2}-4=0  }} \right.\\\\\left \{ {{x=y+4} \atop {3y^{2}+8y+12=0 }} \right.$

$3y^{2}+8y+12=0\\\\D=8^{2}-4*3*12=64-144=-80<0$

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