Решение смотри на фотографии
Пусть скорость лодки - х. ⇒
8/(x-2)+12/(x+2)=2
8x+16+12x-24=2(x²-4)
20x-8=2x²-8
2x²-20x=0 I÷2
x²-10x=0
x(x-10)=0
x₁=0 x₁∉ x₂=10
Ответ: скорость лодки 10 км/ч.
(а) (2x+7)+(-x+12)=14 (б) (-5у+1)-(3y+2)=-9
2x+7-x+12=14 -5y+1-3y-2=-9
x=14-12-7 -8y=-8
x=-5 y=1
1) ((x^(1/2)-y^(1/2))/(x^(3/2)-y^(3/2)))^(-1) = (x^(3/2)-y^(3/2))/(x^(1/2)-y^(1/2)) = (x^(1/2)-y^(1/2)*(x+(xy)^(1/2)+y)/(x^(1/2)-y^(1/2))=x+(xy)^(1/2)+y
2) x+(xy)^(1/2) + y + (xy)^(1/2) = x+2(xy)^(1/2) + y = (x^(1/2)+y^(1/2))^2
3) (x^(1/2)+y^(1/2))^2/(x^(1/2)+y^(1/2))=x^(1/2)+y^(1/2)