Ответ...
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1)10/(a-1)² * (a-1)(a+1)/10=(a+1)/(a-1)
2)6/(a-1)-(a+1)/(a-1)-(2a+2)/(a-1)=(6-a-1-2a-2)/(a-1)=(3-3a)/(a-1)=
=-3(a-1)/(a-1)=-3
(sint-cost)²-2sint*cost=sin²t-2sint*cost+cos²t-2sint*cost=1-2sin2t
3х-1/6х-3 - 1/1-4х^2=х/2х+1
3х-1/6х-3 - 1/1-4х^2 - х/2х+1=0
2/3(-2х+1)=0
2=0
Решений нет