4) ( x/(x²+2x+4) +(x²+8)/(x³ -8) -1/(x-2) ) *( x²(x² -4) -2/(2 -x) ) =
( x/(x²+2x+4) +(x²+8)/(x-2)(x²+2x+4) -1/(x-2) ) *( x²/(x -2)(x+2) +2/(x -2) ) =
( ( x(x-2) +x²+8 -(x²+2x+4))/(x-2)(x²+2x+4) ) *( (x² +2(x+2) )/(x-2)(x+2) ) =
( ( x²-2x +x²+8 -x²-2x-4))/(x-2)(x²+2x+4) ) *( (x² +2x+4 )/(x-2)(x+2) ) =
( ( x²-4x +4))/(x-2)(x²+2x+4) ) *( (x² +2x+4 )/(x-2)(x+2) ) =
( ( x-2)²/(x-2)(x²+2x+4) ) *( (x² +2x+4 )/(x-2)(x+2) ) =1/(x+2).
5) ( 1/(2-a) +(6a-4-a²)/(a³ -8) -(2-a)/(a²+2a+4) ) *((a³ +4a²+8a+8)/(4-4a+a² -a³)) =
( (-a²-2a -4 +6a-4-a²+a² -4a+4) /(a-2)(a²+2a+4) ) *((a³ +8 +4a²+8a)/(4(1-a)+a²(1 -a))) = (-(a²+4) /(a-2)(a²+2a+4) ) *(((a +2)(a²-2a+4)+4a(a+2))/(1-a)(a²+4)) =
(-(a²+4) /(a-2)(a²+2a+4) ) *((a +2)(a²+2a+4)/(1-a)(a²+4)) =(a+2)/(a-1)(a-2).