1.x^5+x^4-6x^3-6x^2+8x+8=0 2.x^5-3x^3+x^2-3=0

 x^5+x^4-6x^3-6x^2+8x+8=0
x^4(x+1) - 6x^2(x+1)+8(x+1)=0
(x+1)(x^4-6x^2+8)=0
x + 1 = 0 
x1 = -1

x^4 - 6x^2 + 8 = 0
t=x^2>0
x^2-6t+8=0
D= 36 - 32  = 4 
√4=2
t1=(6+2)/2=8/2=4
t2=(6-2)/2=4/2=2

x2;3=+-√4=+-2
x4;5=+-√2

x^5 - 3x^3 + x^2 - 3 = 0
x^3(x^2-3)+x^2-3=0
(x^2-3)(x^3+1)=0
x1;2=+-√3   x3=-1