Решений нет, так как √y ≥ 0
-0,8*(-5/6) - 11/12 = 0,8*(5/6) - 11/12 = 4/6 - 11/12 = 8/12 - 11/12 = -3/12 = -1/4 = -0,25
X(x^2 -81) =0
x(x-9)(x+9) =0
x1= 0 x2= 9 x3= - 9
D=An+1 – An = An+4 –An = 4
А6 = А1+5d=–9+5•4=11
(A1+A6)•6
S6 = —————- = (–9+11)•3 = 6
2