<span>(y+1)(x-1)=xy+1+y
x=4(y-x)-x
</span><span>
x=4y-4x-x
x=4y-5x
6x=4y
<u>y=1.5x</u>
</span><span><span>(y+1)(x-1)=xy+1+y</span>
(1.5x+1)(x-1)=x*1.5x+1+1.5x *2
(3x+2)(x-1)=3x²+2+3x
<u>3x²</u>-3x+2x-2=<u>3x²</u>+3x+2
-x-2=3x+2
4x=-4
x=-1
y=-1.5
</span>
2400/2/x-2400/2/(x+200)=0.5
1200/x-1200/(x+200)=0.5
(1200/x-1200/(x+200))*x=0.5*x
240000/(x+200)=0.5x
240000/(x+200)*(x+200)=0.5x*(x+200)
240000=0.5x²+100x
-0.5x²-100x+240000=0
D=-100²-4*(-0.5)*240000=490000
x1=(√490000-(-100))/(2*(-0.5))=-800
x2=(-√490000-(-100))/(2*(-0.5))=600 км в час
(x;y)
х - ось ОХ
у - ось ОУ