Cosx=y
2y^2+y-1=0
D=√9
y=-1
y=0.5
cosx=-1
x=π+2πn
cosx=0.5
x=+-arccos0.5+2πn
x=+-π/3+2πn
32x^5 - 1 = 2^5x^5-1^5 = (2x)^5 - 1^5 = (2x-1)(16x^4+8x^3+4x^2+2x+1)
1) 5a*6b-25a^2-36b^2+5a*6b=60ab-25a^2-36b^2
2) (x-y)(x+y)(x-y)=(x^2-y^2)(x-y)=x^3-x^2y-xy^2+y^3