1. Extreme #181
After standard eliminations we are here:
-- etti on 5 one column must not contain 5; this can only be column 1
S
eliminates 5 from EFG1 and 4 from F1
– ow F must contain 3 all rows contain 3 col 1 must contain 3
r
eliminates 1 from BC1 and 2 from B1
– B2=1 (single), C3=1 (single), eliminates 1 from DF23 and 7 from DEF3
– swordfish 7 (cols) on BCD 789 eliminates 7 from BCD1235
– swordfish 7 (rows) on EGH 245 eliminates 7 from F25
– 2 or F6 must contain 4 (F9 does not)
F
so if G9=4, all rows contain 4, but col 1 does not contradiction to Setti
so G9=1 H9=4
– x-wing 5 on GH25 eliminates 5 from BCDEF 25
– 5 cannot be 6, because this would lead to F6=5, F123=234, no digit left for F9
F
so F6=3
The rest is easy and can even done by the solver