-6a+7b+3a-4b = 3b-3a = 3(b-a)
если а=3,2 , b=4,2 , то 3(b-a) = 3(4.2-3.2) = 3х1 = 3
(1+3а)+(а²-2а)-(2а²-а)=1+3а+а²-2а-2а²+а=
=1+а-а²+а=1+2а-а²
6-4x=4-6*(x-7)
6-4x=4-6x+42
6-4x=46-6x
-4x+6x=46-6
2x=40
x=20
По формуле синуса двойного угла
7/4*cos(x/4) = cos^3(x/4) + 2sin(x/4)*cos(x/4)
cos^3(x/4) + cos(x/4)*(2sin(x/4) - 7/4) = 0
cos(x/4)*(cos^2(x/4) + 2sin(x/4) - 7/4) = 0
1) cos(x/4) = 0; x/4 = pi/2 + pi*k; x1 = 2pi + 4pi*k
2) 1 - sin^2(x/4) + 2sin(x/4) - 7/4 = 0
Умножаем все на -1 и делаем замену sin(x/4) = y
y^2 - 2y + 7/4 - 1 = 0
y^2 - 2y + 3/4 = 0
D/4 = 1 - 3/4 = 1/4 = (1/2)^2
y1 = sin(x/4) = 1 - 1/2 = 1/2; x/4 = (-1)^n*pi/6 + pi*n; x2 = (-1)^n*2pi/3 + 4pi*n
y2 = sin(x/4) = 1 + 1/2 = 3/2 - решений нет, потому что sin x <= 1
Ответ:
x1 = 2pi + 4pi*k;
x2 = (-1)^n*2pi/3 + 4pi*n