Ответ:
1)x=-1/3 2)x=-4/13
Объяснение:
1)3(x²-2)-3x+7-3(x²-2x)=0
3x²-6-3x+7-3x²+6x=0
3x=-1
x=-1/3
2)-(x²-2)-0.3x+7x+(x²-0.2x)=0
-x²+2-0.3x+7x+x²-0.2x=0
6.5x=-2
x=-2*10/65=-20/65=-4/13
Sin(60°+a)sin(60°-a) = (1/2)*[cos(60° + α - 60° + α<span>) -
- cos(</span>60° + α + 60° - α)] = (1/2)*[cos2α - cos(120°)] =
= (1/2)*[cos2α + cos(60°)] = (1/2)*[cos2α + 1/2)] = (1/2)*cos2α + 1/4
(3^4/10-10^-3•10^2):(2/5)^2=(81/10-10^-1):4/25=(81/10-1/10)•25/4=8•25/4=2•25=50