1. b) (2/(7y+x))(x-2/7y) =
2*(x-2) /(7y+x)*7y =(2x-4)/(49y²+7xy)
a) (4x-0.2y)² =16x² -1.6xy +0.04y²
2. (x-2)(x+2) -(x-1)² =x² -5
x² -4 -(x² -2x +1) =x² -5
x² -4 -x² +2x -1 =x² -5
2x -5 =x² -5
-x² +2x -5 +5 =0
2x -x² =0
x(2 -x) =0
x =0
2 -x =0
x =2
3. (a² +10a +25)/(a +5) при a =2.5
(a +5)² /(a +5) =a +5 =2.5 +5 =7.5
задание прикреплено))))))))))))))))))))
1 - cos(2x) = sin²x + cos²x - (cos²x - sin²x) = sin²x + cos²x - cos²x + sin²x = 2sin²x
1+2sinx=2cos2x
1+2sinx=2(1-2sin^2x)
1+2sinx=2-4sin^2x
4sin^2x+2sinx-1=0
sinx=(-1+-sqrt(5))/4 sinx>=0
sinx=(sqrt(5)-1)/4
x=(-1)^k*arcsin(sqrt(5)-1)/4)+Пk
sinx<0
1-2sinx=2-4sin^2x
4sin^2x-2sinx-1=0
x=(1+-sqrt(5))/4
x=1-sqrt(5))/4
x=(-1)^larcsin((1-sqrt(5)/4)+Пk