Решение
1) cos720+tg 30 ctg 210+sin 120 = сos2*360° + tg30°ctg(180° + 30°) +
+ sin(90° + 30)° = 1 + 1/√3*ctg30° + sin30° = 1 + (1/√3)*(√3) + 1/2 = 1 + 1 + 1/2 = 2(1/2)
<span>tg0 </span>°<span>- 2ctg90</span>° <span>- sin0</span>° <span>- 3cos90</span>° = 0 - 2*0 - 0 - 3*0 = 0
Log9 (x-1)=1
9ˇ(1)=x-1
9=x-1
x=9+1,x=10
loga (b) = c, ecli aˇc =b, naprimer log5 (25)=2, potomy čto 5ˇ2 =25.
27y^4-18 y^2=
Вынесем 9y² за скобку и получим
9y²(3y-2)
x^2-3x+1=0
D=(-3)^2-4*1*1=5
x1,2=3 + или -корень из 5
__________________
2