::::::::::::::::::::::решение
5x^2 - 4x - 1 = 0
D = 16 + 20 = 36
x1 = (4 + 6)/10 = 1
x2 = (4 - 6)/10 = - 1/5 = - 0,2
Ответ: у = 4* (-2,5) -3 = -1,5
Cos<span>^2 <span>α</span>+Ctg^<span>2 <span>α</span>-1/Sin<span>^2 <span>α = Cos^2 α+Ctg^2 α-1-Ctg^2 α = Cos^2 α-1= Cos^2 α-Sin^2 α-Cos^2 α = -Sin^2 α
Вроде так. </span></span></span></span>