(60-6)/(x-3)-60/x=0.5 54/(x-3)-60/x=0.5 (54/(x-3)-60/x)*x=0.5*x (-6x+180)/(x-3)=0.5x (-6x+180)/(x-3)*(x-3)=0.5x*(x-3) -6x+180=x^2/2-3x/2 -x^2/2-9x/2+180=0 -0.5x^2-4.5x+180=0 D=-4.5^2-4*(-0.5)*180=380.25 x1=(√380.25-(-4.5))/(2*(-0.5))=-24 x2=(-√380.25-(-4.5))/(2*(-0.5))=15 Ответ : 15 километров в час