Question

Решить систему уравнений методом подстановки:
{x-y=4
X^2+y^2=8​

Answer 1

Відповідь:

x = 2

y = -2

Пояснення:

$\left \{ {{x-y=4} \atop {x^{2}+ y^{2}=8}} \right. \\\left \{ {{x=4+y} \atop {x^{2}+ y^{2}=8}} \right. \\\\\left \{ {{x=4+y} \atop {(4+y)^{2}+ y^{2}=8}} \right. \\\\\left \{ {{x=4+y} \atop {16+8y+y^{2}+ y^{2}=8}} \right. \\\\\left \{ {{x=4+y} \atop {2y^{2}+8y+8=0}} \right. \\\\D=8^{2} -4*2*8=64-64=0 \\y=\frac{-8+0}{2*2} =-2\\x=4+(-2)=2$