-х2-4х+12меньше или равно 0
под корнем Д=16-4*-12=8
х1=2
х2=-6
-5x - 9 = -6
-5x = -6 + 9
-5x = 3
x = 3 : (-5)
x = - 3/5
x = -0,6
-2x - 3 = 1
-2x = 1 + 3
-2x = 4
x = 4 : (-2)
x = -2
10x + 1 = 6x
10x - 6x = -1
4x = -1
x = -1 : 4
x = -0,25
1) 1 - Ctg T = 1 - CosT\SinT = ( SinT - CosT) \ SinT
2) 1 - TgT = 1 - SinT\CosT = ( CosT - SinT) \ CosT
3) (SinT - CosT) \ SinT ) : ( CosT - SinT ) \ CosT = ( - CosT ) : SinT = ( - Ctg T)