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
-0,4а (2а^2+3)(5-3а^2) =
-0,4а (10а^2-6а^4+15-9а^2) =
-0,4а (-6а^4+а^2+15) =
<span>2,4а^5 - 0,4а^3 - 6а
</span>
...
х + 6/10х +2/3х=680
30/30х + 18/30х + 20/30х = 680
68/30 х =680
х = 680 : 68/30
х = 680/1 * 30/68
х = 10/1 * 30/1
х = 10 * 30
х = 300
2^(2-log2 5) = 2^2 / 2^log2 5 = 4 / 5 = 0.8