sin3xcosx-cosxsin3x=sin2x
то есть sin2x=<1/2
это равносильно
2x принадлежит [5П/6+2Пк;13П/6+2Пк]
тогда x [5П/12+Пк;13П/12+Пк]
D=36-20=16
x1=4-6/2=-2/2=-1
x2=-4-6/2=-10/2=-5
4<span>√3x-<span>√4*3x-<span>√25*3x= 4<span>√3x-2<span>√3x-10<span>√3x=-8<span>√3x</span></span></span></span></span></span></span>
<span><span><span><span><span><span><span>3<span>√4*3+2<span>√3-2<span>√9*3=3*2<span>√3+2<span>√3-2*3<span>√3=6<span>√2+2<span>√3-6<span>√3=2<span>√3</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
<span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span>(<span>√4*2-<span>√4*6)*<span>√2=(2<span>√2-2<span>√6)*<span>√2=2*2-2<span>√6*2=4-2<span>√12=4-4<span>√3</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
<span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span>√18*3-<span>√8*3+<span>√50*3=<span>√9*2*3-4<span>√3+<span>√25*2*3=3<span>√6-4<span>√3+5<span>√6=8<span>√6-4<span>√3</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
<span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span><span>√16*3-2<span>√3(2-5<span>√3*4)=4<span>√3-2<span>√3(2-10<span>√3)=4<span>√3-4<span>√3+20*3=60</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
Бригада 1:
Работала 4 д.
Уложила х+500 кв. м. асфальта
Бригада 2:
Работала 6 д.
Уложила х кв. м.
Две бригады уложили 6200 кв. м, что равно х+х+500
х+х+500=6200
2х=5700
х=2850
Итого, бригада 1 уложила 3350 кв. м, а бригада 2 - 2850 кв. м асфальта
Пусть скорость катера - х . 2 ч 15 мин =2_1/4 ч=(9/4) ч.
30/(27+х)+30/(27-х)=9/4
810-30x+810+30x=(9/4)*(27^2-x^2)
1620=(9/4)*(729-x^2) I*(4/9)
720=729-x^2
x^2=9
x=3
<span>Ответ: скорость течения реки 3 км/ч.</span>