Bitcoin miners attack with 51% majority – question on the role of user-activated soft forks as defense tactics

For example, if a mining company alone owns 52% of the hash power of the entire network, that party can block transactions and try to build a forked, longer chain over time, right? As far as I know, this can take several weeks with only 52% hash power …

Can someone please explain how the "User-activated soft-fork" feature can be a tool for network users to rescue and retain the "current" Blockchain version and escape the attacker? How would this ideally run from the perspective of the user (full node user)?

thanks

postgresql – can I be helped? my question should = something like .000534 but I get 0

can be helped my query should = something like .000534 but I get 0.
Could you have a suggestion to help me?
Thank you very much

psql -Upostgres -dcans -c "select (choose COUNT () FROM brd.gaf_info where can_piecesre_sucbattery = & # 39; pr & # 39; and
gaf_start_date> & # 39; 2019-11-13 01: 01: 01.754 & # 39; /
(Select COUNT (
) FROM brd.gaf_info where gaf_start_date> & # 39; 2019-11-13 01: 01: 01.754 & # 39;); "

linear algebra – question about the reduction formula for characteristic polynomial

Q) Leave $ p (G, x) $ is the characteristic polynomial of the adjacency matrix of a graph $ G $, Accept $ v_i $ is a vertex of degree $ 1 $ from $ G $ and $ v_j $ is $ v_i's $ Neighbor and suppose $ G_1 = G – {v_i }, G_2 = G – {v_i, v_j } $, then show it

$$ p (G, x) = xp (G_1, x) -p (G_2, x) $$

It must be a simple extension of the determinant along a row / column that I can not think of. Thank you very much.