1/2xy - (2x+3y)/6xy 

если х= √5 - 1

y=1/12 

esli  sqrt(5)-1 y=1/12

1/2xy-1/3y-1/2x => (6/sqrt(5)-1)-4-(1/2sqrt(5)-1)

5/sqrt(5)-1-4

5(sqrt(5)+1)/(sqrt(5)-1)*sqrt(5)-1-4

(5sqrt(5)+5)/4-4=> 5(sqrt(5)+1)-16/4=(5sqrt(5)-11)/4