1. a) (2x +1)(2x -1) =4x² -1
b) (a +5)² =a² +10a +25
в) (3x -y)² =9x² -6xy +y²
2. a) (x +1)² -2x(1 -x) =x² +2x +1 -2x +2x² =3x² +1
b) 3(a-b)² -3b² =3a² -6ab + 3b² -3b² =3a² -6ab = 3a(a - 2b)
3. a) a² -25=(a -5)(a +5)
b) b² +6b +9 =(b +3)² =(b + 3)(b +3)
в) x^3 -4x =x(x² -4)=x(x -2)(x +2)
Cos123°=cos(90+33°)........... вот так
Y - 4y = (1 - 4)y = - 3y
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Это 3 номер, правильный вариант 1
x^4-17x^2+16 = 0
t^2-17t+16 = 0
t= 16
t = 1
x^2 = 16
x^2 = 1
x = 4
x = –4
x = 1
x = –1