а³в³-8=(ав-2)(а²в²+2ав+4)
Lgx + lgx² + lgx³ = 6
ОДЗ: x > 0
lgx + 2lgx + 3lgx = 6
6lgx = 6
lgx = 1
x = 10
2,3-0.5x=4.9+0.8x
0.8x+0.5x=2.3-4.9
1.3x=-2.6
x=-2.6/1.3
x=-2
1)Cos2a/Cosa-Sina= Cos^2-Sin^2/Cosa -Sina= Cosa-Sina
3)Sin^2*Ctga/Sin2a=Sin^2* (Cosa/Sina)/2sinacosa=(Sina^2*Cosa/Sina)/2sinacosa=SinaCosa/2sinacosa=1/2