mi servirebbe solo il 156
√((1 - 2/7)·((7/3 + 1/15)·(5/6 + 4/3 - 1 - 3/4)^2 - (7/5 - 19/15)^2·(15/4)))=
=√(5/7·(12/5·(5/12)^2 - (2/15)^2·(15/4)))=
=√(5/7·(12/5·(25/144) - 4/225·(15/4)))=
=√(5/7·(5/12 - 1/15))=
=√(5/7·(7/20))=
=√(1/4)=
=1/2