My recent winter holidays were a lot of fun. I tried to visit as many places as I could and to do a lot of different things. Even though the weather wasn't very nice, it didn't make me feel sad. I went to the mall and to the skating-rink with my family and friends. It's always interesting to learn something new, so I also visited the movies and watched some great films. And then, of course, there were New Year and Christmas, which are both my favourite holidays. We had a gorgeous Christmas-tree decorated with toys and Christmas lights. On the first day of new year I got many presents from my family and relatives. After all, it was just great to take some time off from school and to sleep till noon. I really enjoyed my winter holidays.
1)3(2x-7)=9 2)6(z-1)=18 3)3(x-5)=x+3 4)50-7e-16=3e-16 5)Не могу понять!
6x-21=9 6z-6=18 3x-15=x+3 -7e-3e=-16-50+16
6x=9+21 6z=18+6 3x-x=3+15 -10e=-50
6x=30 6z=24 2x=18 e=-5
x=5 z=4 x=9 6)-(b+5)=16 7)-(4c-7)=5c+(11-7c)
-b-5=16 -4c+7=5c+11-7c
-b=16+5 -4c-5c+7c=11-7
-b=21 -2c=3
c=1,5
2sin x*cos x - 2√3*(cos x*cos(7П/6) - sin x*sin(7П/6)) = 3cos x
2sin x*cos x - 2√3*(cos x*(-√3/2) - sin x*(-1/2)) = 3cos x
2sin x*cos x + 2√3*√3/2*cos x - 2√3/2*sin x = 3cos x
2√3*√3/2*cos x = 3cos x, их можно сократить.
2sin x*cos x - √3*sin x = 0
sin x*(2cos x - √3) = 0
1) sin x = 0; x = П*k, k € Z. На отрезке [-3П/2; 0] будут корни x1 = -П; x2 = 0
2) cos x = √3/2; x = +-П/6 + 2П*n, n € Z. На отрезке [-3П/2; 0] будет x3 = -П/6
ответ: x1 = -П; x2 = 0; x3 = -П/6