1. +*+=+
2. +*+=+
3. +
4. +
Ответ:
-4
Объяснение:
-2(x+3)=2x-1
-2x-6=2x-1
-2x-6-2x+1=0
-4x-5=0 / *(-1)
4x+5=0
a=0;b=4;c=5
D=b^2-4ac
D=16-4*0*5
D=16
x1,2=-b+/-корень D / 2a
x1,2=-4+/-4 / 2
x1=-8/2; x1=-4
x2=0/2; x2=0
18°=π/1063°=7π/20
cos π/10 * cos 7π/20 + sin π/10 * sin 7π/20 = cos (π/10 - 7π/20)по формуле cos a*cos b+sin a*sin b=cos(a-b)cos (π/10 - 7π/20) = cos (2π/20-7π/20)=cos(-5π/20)=cos(-π/4)=cos(7π/4)=√2/2