Question

помогите пожалуйста решить 3 и 4 задание

Answer 1

Длина - x ,   ширина y
x*y = 300
(x + 5)(y - 5) = 250
xy - 5x + 5y - 25 = 250
xy  - 5(x - y) - 25 = 250
300 - 5(x - y) - 25 = 250
- 5(x - y) = - 25
x - y = 5$left { {{x-y=5} atop {xy=300}} right.\\ left { {{x=5+y} atop {(5+y)y=300}}\\ left { {{x=5+y} atop { y^{2}+5y-300=0 }} right. right.\\ left { {{y _{1} =15} atop {x _{1} =5+15}} right.\\ left { {{y _{1} =15} atop {x _{1} =20}} right.\\ left { {{y _{2} =-20} atop {x _{2}=5-20 }} right\\ left { {{y _{2} =-20} atop {x _{2}=-15 }} right. .$
Ответ: (20 ;15) , (- 15 ; - 20)


$left { {{(x + 3y) ^{2}=16 } atop {x=3y-2}} right. \\ left { {{x+3y =4} atop {x=3y-2}} right.\\ left { {{3y-2+3y=4} atop {x=3y-2}} right.\\ left { {{6y=6} atop {x=3y-2}} right.\\ left { {{y=1} atop {x=1}} right. \\ left { {{x+3y=-4} atop {x=3y-2}} right.\\ left { {{3y-2+3y=-4} atop {x=3y-2}} right.\\ left { {{6y=-2} atop {x=3y-2}} right.\\ left { {{y=- frac{1}{3} } atop {x=-3}} right.$
Ответ. (1 , 1),(- 3 ; - 1/3)