S=u*t
u=70км/ч = 70*1000/3600= 19,45м/с
t=60+12=72сек
s=72*19.45= 1400 метров
(х-9)²=(х-3)²
х²-18х+81=х²-6х+9
х²-18х+81-х²+6х-9=0
-12х+72=0
-12х=-72
х=6
(x-1)(x+1)/[(1-x)(1+x+x²)]-x²/(1+x+x²)=-(x+1)/(1+x+x²)-x²/(1+x+x²)=
=(-x-1-x²)/(1+x+x²)=-(1+x+x²)/(1+x+x²)=-1
2(3√х-5х)+3(7х-2√х)= 6√х-10х+21х-6√х=11х