3tg^2(x/3)-2tgx/3-1=0
tgx/3=t
3t^2-2t-1=0
t=1/3(1+-2)
t1=-1/3
t2=1
tgx/3=1 x=3П/4+3пk
tgx=-1/3 x=3arctg(-1/3)+3Пk
=2/3 + 44/9 = 6/9 + 44/9 = 50/9 =
{10-5x>-15⇒5x<10+15⇒5x<25⇒x<5
{-72+12x<0⇒12x<72⇒x<72:12⇒x<6
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Ответ 2