2+81-45x+8=0
-45x+91=0
-45x=-91
x=2,02
2х-у=3
3х+5у=-2
у=2х-3
3х+5(2х-3)=-2
у=2х-3
3х+10х-15=-2
у=2х-3
13х=13
у=2х-3
х=1
у=2*1-3
х=1
у=-1
х=1
Проверка:
2*1-(-1)=3
<span>3*1+5*(-1)=-2</span>
2cos(5a+3a)/2*cos(5a-3a)/2=2cos4a*cosa.
![\displaystyle (8x^2 - 3x+1)^2 = 32x^2 - 12x+1\\ \\ (8x^2 - 3x+1)^2 -32x^2 +12x - 1 = 0\\ \\ \ z =8x^2 -3x \\ \\ -(4z+1) +(z^2 +2z+1)=0\\ \\ -4z-1+z^2 +2z+1=0\\ \\ -2z+z^2 =0\\ \\ -z *(2-z)=0\\ \\ -z = 0\\ \\ 2-z=0\\ \\ z = 0 \\ z=2\\](https://tex.z-dn.net/?f=+%5Cdisplaystyle+%288x%5E2+-+3x%2B1%29%5E2+%3D+32x%5E2+-+12x%2B1%5C%5C+%5C%5C+%288x%5E2+-+3x%2B1%29%5E2+-32x%5E2+%2B12x+-+1+%3D+0%5C%5C+%5C%5C+%5C+z+%3D8x%5E2+-3x+%5C%5C+%5C%5C++-%284z%2B1%29+%2B%28z%5E2+%2B2z%2B1%29%3D0%5C%5C+%5C%5C+-4z-1%2Bz%5E2+%2B2z%2B1%3D0%5C%5C+%5C%5C+-2z%2Bz%5E2+%3D0%5C%5C+%5C%5C+-z+%2A%282-z%29%3D0%5C%5C+%5C%5C+-z+%3D+0%5C%5C+%5C%5C+2-z%3D0%5C%5C+%5C%5C+z+%3D+0+%5C%5C+z%3D2%5C%5C++)
![\displaystyle 8x -3 =0\\ \\ 8x^2-3x -2 =0 \\ \\ 1) x= 3/8\\ \\\\ 2)\ 8x^2-3x -2 \\ D= (-3)^2 - 4 *8*(-2) =73 \\ \\ x _1_,_2 =\frac{3б\sqrt{73}}{16} \\ \\](https://tex.z-dn.net/?f=+%5Cdisplaystyle++8x+-3+%3D0%5C%5C+%5C%5C+8x%5E2-3x+-2+%3D0+%5C%5C+%5C%5C++1%29++x%3D+3%2F8%5C%5C++%5C%5C%5C%5C++2%29%5C+8x%5E2-3x+-2+%5C%5C+D%3D+%28-3%29%5E2+-+4+%2A8%2A%28-2%29+%3D73+%5C%5C+%5C%5C+x+_1_%2C_2+%3D%5Cfrac%7B3%D0%B1%5Csqrt%7B73%7D%7D%7B16%7D+%5C%5C+%5C%5C+++)
ответ: x 1 = ( 3 - sqrt(73)) / 16 , x2 =0 , x3=3/8 , x4= (3+sqrt(73))/16