Помогите прошу, через 9 часов сдаю

Ответ

Проверено экспертом

Автор - Universalka

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

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

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 .