A (a-2)(a+2)=a (a в квадрате -4)=а в 3 степени -4а
X^3+y^3=(x+y)(x^2-xy+y^2)
x^6+y^6+x^2+y^2=(x^2+y^2)(x^4-x^2y^2+y^4)+(x^2+y^2)=(x^2+y^2)(x^4-x^2y^2+y^4+1)
4cosx - 4sinx - 4sin2x = 0
4cosx - 4sinx - 8sinxcosx = 0 | : 8cosx
2 - 4tgx - tgx = 0
2 - 5tgx = 0
-5tgx = -2
tgx = 2/5
x = arctg2/5 + Pi*n, n € Z
<span>cos4x=cos^2(2x)-sin^2(2x)</span>