Cos^2 a = 1 - 16\25
cosa = -3\5
tga = 4\3
ctga = 3\4
3/7*y-9=-12+y/7
2y/7+3=0
3y/7-9=y-84/7
Переумножаем крест накрест.
3(y-21)/7=y-84/7
y=-21/1
(а+1-3а)(а+1+3а)=(1-2а)(1+4а)
A) a^2+2ax+x^2
b) m^2-2mn+n^2
в) 49-14a+a^2
г) 144-24p+p^2
D) 4a^2+4a+1
e) 49y^2+72y+36
ё) (5x-3a)^2=25x^2-30ax+9a^2
ж) (4n-3m)^2=16n^2-24mn+9m^2
з) x^4+2x^2+1