71371371 ......................................
...................................................................
(3-5х)(1-2х+3х^2)=3-6х+9х^2-5х+10х^2-15х^3=3-11х+19х^2-15х^2
3sqrt(343*0,125)=3sqrt(0,25*0,5*7*49)=3sqrt(3,5)*0,5*7=10,5sqrt(3,5)
<span>Воспользуемся формулой суммы тангенсов:</span>
<span>tg(x/3 + pi/4)+tg(x/3 - pi/4)=sin(2x/3)/(cos(x/3+pi/4)*cos(x/3-pi/4)=</span>
<span>sin(2x/3)/(0.5(cos(pi/2)+cos(2x/3))=2tg(2x/3)</span>