4cos^2(x)-4sinx-5=0
4-4sin^2(x)-4sinx-5=0
4sin^2(x)+4sinx+1=0
(2sinx+1)^2=0
2sinx+1=0
2sinx=-1
sinx=-1/2
x=(-1)^k * arcsin(-1/2) + pi*k
x=(-1)^(k+1) * pi/6 + pi*k
{2x+3y-2z =10
{4x-2y +z= 9
{x-3y +4z=1
{2x+3y-2z=10
{z= 9-4x+2y
{x-3y +4z=1
{2x +3y -2(9-4x+2y) =10
{x-3y +4(9-4x+2y)=1
{2x+3y -18+8x-4y=10
{x-3y +36-16x +8y=1
{10x -y= 10+18
{-15x +5y=1-36
{y=10х-28
{-15x +5y=-35
-15x +5(10х-28) =-35
-15x +50х - 140=-35
35х= -35+140
35х=105
х= 105:35
х=3
у=10*3-28= 2
z=9-4*3 +2*2 = 9-12+4= 1
Ответ: x=3 ; у= 2 ; z=1.