Question

2x²+y=4; x+y=3 решите систему уравнений

Answer 1

$- \left \{ {{2 x^{2} +y= 4} \atop {x+y =3}} \right.$
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$\left \{ {2 x^{2} -x=1} \atop {y=3-x}} \right.$

$\left \{ {{2 x^{2} -x-1=0} \atop {y=3-x}} \right.$

$\left \{ {{x=1} \atop {y=3-1}} \right.$        $\left \{ {{x=-0,5} \atop {y=3+0,5}} \right.$

$\left \{ {{x =1} \atop {y=2}} \right.$            $\left \{ {{x= - 0,5} \atop {y = 3,5}} \right.$
Корни найдены так:
2x² - x - 1 = 0
D = (-1)² - 4*2*(-1) = 1 + 8 = 9 = 3²
X₁ = (1+3)/4 = 1
X₂ = (1 - 3)/4 = - 0,5