А) cos(a)-cos(b)=-2sin( a+b/2)sin( a-b/2)
cos36°-cos24°=-2sin(36°+24°/2)sin(36°-24°/2)=
-2sin30°sin4°=-2*1/2*sin4°=-sin4°
<span>{(x+3)(2x-4)>0
{6(x-4)>x-5(x+4)
{2(x+3)(x-2)>0
{6x-24>x-5x-20
{(x+3)(x-2)>0
{x>0.4
{x</span>∈(-∞;-3)U(2;+∞)
{x∈(0.4;+∞)
ответ x∈(2;+∞)
{4x-y=6
{4x²-y²=8
y=(4x-6)
4x²-(4x-6)²=8
4x²-16x²+48x-36-8=0
-12x²+48x-44=0
3x²-12x+11=0
D==144-12*11=12
x=(12+√12)/6=(12±2√3)/6=(6±√3)/3
x1=(6+√3)/3
y1=(4(6+√3)/3)-6==(24+4√3-18)/3=(6+4√3)/3
x2=(6-√3)/3
y2=(4(6-√3))/3)-6=(24-4√3-18)/3=(6-4√3)/3