2cos²x=1+4sin4x
2(1+cos2x/2)=1+8sin2xcos2x
1+cos2x=1+8sin2xcos2x
1+cos2x-1+8sin2xcos2x=0
cos2x+8sin2xcos2x=0
cos2x(1+8sin2x)=0
cos2x=0
2x= π/2+πk |:2
x= π/4+πk/2
sin2x=-1/8
2x=(-1)^k+1 arcsin1/8+πn |:2
x=(-1)^k+1 arcsin1/16+πn/2
(2х+у)²=4х²+2*2х*у+у²=4х²+4ху+у²
4(х-0,5у)²=4(х²-1ху+0,25у²)=4х²-4ху+1у²
16x^2+16x+3=0
D=256-4*16*3=8^2
x1=(-16+8)/32=-1/4
x2=(-16-8)/24=-3/4