3)
x - 7 = 14
x = 14 + 7
x = 21
4)
21 - 5x = 6
-5x = 6 - 21
-5x = -15
x=3
5)
x + x + 4 + x = 16
3x = 16 - 4
3x = 12
x = 12/3
x = 4
6)
<span>х + 5 + х + 6 = 21
</span>2x = 21 - 11
2x = 10
x = 10/2
x = 5
7)
<span>х + 2х - 5 = 40
</span>3x = 40 + 5
3x = 45
x = 45/3
x = 15
8)
0.1x = 3
x = 3/0.1
x = 3 * 10
x = 30
а) 2cos150° - 3tq405° =2cos(180° -30°) -3tq(360°+45°) = -2cos30° -3tq45° =
-2*√3/2 -3*1 = -√3 - 3.
б) sin 7π/6 - cos2π/3 =sin(π +π/6) -cos(π-π/3) = -sinπ/6 +cosπ/3 = -1/2 +1/2 = 0.
Решение смотри на фотографии
Sinacosb+cosasinb-sinacosb=cosasinb
1/4=0.25\%-того что извлекёт карточку №3 последний