(х - 2)^2 + 8x = (x - 1)([x + 1)
x^2 - 4x + 4 + 8x = x^2 - 1
x^2 - x^2 + 4x = - 4 - 1
4x = - 5
x = - 1,25
(с²-2с+1²)-1²+12=(с-1)²+11>0
(c-1)²≥0
11>0
(c-1)²+11>0
Пишу предложения...использую подсказки...
<span>arccos (sin(-п/4))=arccos(-√2/2)=pi-arccos(√2/2)=pi-pi/4=3pi/4</span>