(sin2x + sin4x)^2 + (cos2x + cos4x)^2 = 4(cosx)^2
(sin2x)^2+2sin2xsin4x+(sin4x)^2 + (cos2x)^2+2cos2xcos4x+(cos4x)^2=4cos^2x
((sin2x)^2+(cos2x)^2)+((sin4x)^2 + (cos4x)^2)+2sin2xsin4x+2cos2xcos4x=4cos^2x
1+1+2(sin2xsin4x+cos2xcos4x)=4cos^2x
sin2xsin4x+cos2xcos4x=2cos^2x-1
cos(4x-2x)=2cos^2x-1
cos2x=cos2x
Доказано
У= 5*3,6:4
у=4,5
крест на крест
4x^2+4x+1=0
Д=16-16=0
х=-4/8=-0.5
_______________________
![2 \times |4x + 5| = 6 \\ \\ |4x + 5| = 3 \\ \\ a) \: \: 4x + 5 = 3 \\ 4x = 3 - 5 \\ 4x = - 2 \\ x = - \frac{2}{4} = - 0.5 \\ \\ b) \: \: 4x + 5 = - 3 \\ 4x = - 3 - 5 \\ 4x = - 8 \\ x = - \frac{8}{4} = - 2 \\](https://tex.z-dn.net/?f=2+%5Ctimes++%7C4x+%2B+5%7C++%3D+6+%5C%5C++%5C%5C++%7C4x+%2B+5%7C++%3D+3+%5C%5C++%5C%5C+a%29+%5C%3A++%5C%3A+4x+%2B+5+%3D+3+%5C%5C+4x+%3D+3+-+5+%5C%5C+4x+%3D++-+2+%5C%5C+x+%3D++-++%5Cfrac%7B2%7D%7B4%7D++%3D++-+0.5+%5C%5C++%5C%5C+b%29+%5C%3A++%5C%3A+4x+%2B+5+%3D++-+3+%5C%5C+4x+%3D++-+3+-+5+%5C%5C+4x+%3D++-+8+%5C%5C+x+%3D++-++%5Cfrac%7B8%7D%7B4%7D++%3D++-+2+%5C%5C+)
ОТВЕТ: - 2 ; - 0,5
______________________________
<span>2.3х-1.4+2.8-0.7х=1.4
23x-14+28-7x=14
16x=0
при x=0</span>