Sin6x-sin3x=0
2sin3x*cos3x -sin3x=0
sin3x(2cos3x-1)=0
sin3x=0
3x=πk
x=πk/3
____
cos3x=1/2
3x=±π/3+2πk
x=±π/9+2πk/3 k€z
A1 = - 4
d = 2
Sn = 84
n = ?
(2a1 + d(n - 1))/2*n = 84
( - 8 + 2(n - 1))/2*n = 84
(- 8 + 2n - 2)/2*n = 84
(2n - 10)/2*n = 84
(n - 5)*n = 84
n^2 - 5n - 84 = 0
D = 25 + 4*84 = 361 = 19^2
n1 = (5 + 19)/2 = 12
n2 < 0 не удовлетворяет
ОТВЕТ
12
1) 2x-1=3
3-1=2x
2x-3•2x=59
59+x+5=8:x+5=43
43-1-x=2
2•1+x=2
16 * 1\8 + 2 * (-1\6) = 2 - 1\3 = 1 3\3 - 1\3 = 1 2\3