Question

Помогите прошу, через 9 часов сдаю

Answer 1

$\left \{ {{x+y=-2} \atop {x^{2}-2xy+y^{2}=36}} \right.\\\\\left \{ {{x+y=-2} \atop {(x-y)^{2} =36}} \right. \\\\\left \{ {{x+y=-2} \atop {x-y=-6}} \right.\\\\\left \{ {{x=y-6} \atop {y-6+y=-2}} \right.\\\\\left \{ {{x=y-6} \atop {2y=4}} \right.\\\\\left \{ {{y=2} \atop {x=2-6=-4}} \right.$

$2)\left \{ {{x+y=-2} \atop {x-y=6}} \right.\\\\\left \{ {{x=y+6} \atop {y+6+y=-2}} \right.\\\\\left \{ {{x=y+6} \atop {2y=-8}} \right.\\\\\left \{ {{y=-4} \atop {x=-4+6=2}} \right.$

Ответ : (2 ; - 4) , (- 4 ; 2)

$2)\left \{ {{xy-3y^{2}=-24}|*(-1) \atop {xy+2y^{2} =21}} \right.\\\\+\left \{ {{-xy+3y^{2}=24 } \atop {xy+2y^{2}=21 }} \right.\\--------\\5y^{2}=45\\y^{2} =9\\1)\left \{ {{y=-3} \atop {x*(-3)+2(-3)^{2} =21}} \right. \\\\\left \{ {{y=-3} \atop {-3x+18=21}} \right.\\\\\left \{ {{y=-3} \atop {x=-1}} \right.$

$2)\left \{ {{y=3} \atop {x*3+2*3^{2} =21}} \right.\\\\\left \{ {{y=3} \atop {3x+18=21}} \right.\\\\\left \{ {{y=3} \atop {x=1}} \right.$

Ответ : (- 1 ; - 3) , (1 ; 3)

3) a - длина , b - ширина

S = a * b = 20

P = 2(a + b) = 18

$\left \{ {{a*b=20} \atop {2(a+b)=18}} \right.\\\\\left \{ {{a*b=20} \atop {a+b=9}} \right.$

По теореме Виета одна из сторон 4 см, а другая 5 см .