1/2 + (5/7·(- 21/10))^2 + (15/4 + 8/5 - 7/9/(- 1/3 + 5/4 - 8/15 - 1/20)^2) - 6/5=
=1/2 + (- 3/2)^2 + (15/4 + 8/5 - 7/9/(1/3)^2) - 6/5=
=1/2 + 9/4 + (15/4 + 8/5 - 7/9/(1/9)) - 6/5=
=1/2 + 9/4 + (15/4 + 8/5 - 7) - 6/5=
=1/2 + 9/4 + (- 33/20 )- 6/5=
=- 1/10