1) ........=3х+9-12+3х-х-3=5х - 6
2) ........=3х+15-4+х-х-3х-3=8
3) ........=2х+8-6+3х-х-4=4х - 2
4) ........=х+1-10+5х-5х-х-5= - 14
5) ........=х+3-2+х-х-4=х-3
6) ........=4х+12-5+х-х-4=4х+3
7) ........=3х+9-4+4х-4х-3х-1=4
8) ........=5х+25-9+3х-х-3=7х+13
9) ........=2х+4-10+5х-5х-2х-1= - 7
10) .......=2х+8-20+4х-4х-2х-3= - 15
AH=AB/2 =35
tg(C/2)=AH/CH=35/35√3=1/√3
C/2=30
C=2*30=60
Ответ: 60 градусов.
Пусть x-сколько цветов всего на клумбе.Составим уравнение:
9+7=x
x=9+7,
x=16.
Ответ:x=16
15+3=18 км/ч-скорость по течению
15-3=12(км/ч)-скорость против течения
V cp=
![\frac{S0}{t0}](https://tex.z-dn.net/?f=+%5Cfrac%7BS0%7D%7Bt0%7D+)
S0=S1+S2=2S
Vcp=
![\frac{2S}{t0}](https://tex.z-dn.net/?f=+%5Cfrac%7B2S%7D%7Bt0%7D+)
t0=t1+t2
t1=
![\frac{S}{V1}](https://tex.z-dn.net/?f=+%5Cfrac%7BS%7D%7BV1%7D+)
t2=
![\frac{S}{V2}](https://tex.z-dn.net/?f=+%5Cfrac%7BS%7D%7BV2%7D+)
![t0= \frac{S}{18} + \frac{S}{12} =S*( \frac{1}{18} + \frac{1}{12} )=S*( \frac{2}{36} + \frac{3}{36})= \\ \\ \frac{5S}{36}](https://tex.z-dn.net/?f=t0%3D+%5Cfrac%7BS%7D%7B18%7D+%2B+%5Cfrac%7BS%7D%7B12%7D+%3DS%2A%28+%5Cfrac%7B1%7D%7B18%7D+%2B+%5Cfrac%7B1%7D%7B12%7D+%29%3DS%2A%28+%5Cfrac%7B2%7D%7B36%7D+%2B+%5Cfrac%7B3%7D%7B36%7D%29%3D+%5C%5C++%5C%5C++%5Cfrac%7B5S%7D%7B36%7D++)
Vcp=
![\frac{2S}{ \frac{5S}{36} } = \frac{2*36}{5} = \frac{72}{5} =14.4](https://tex.z-dn.net/?f=+%5Cfrac%7B2S%7D%7B+%5Cfrac%7B5S%7D%7B36%7D+%7D+%3D+%5Cfrac%7B2%2A36%7D%7B5%7D+%3D+%5Cfrac%7B72%7D%7B5%7D+%3D14.4)
<em>Ответ:средняя скорость равна</em>
14.4<em>км/ч.</em>