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  • 17 votes cast
Apr
6
awarded  Popular Question
Mar
29
revised show $\sum_{j=0}^n (-1)^j {n \brack j}_q =0$ for n odd
added 10 characters in body; edited tags
Mar
29
asked show $\sum_{j=0}^n (-1)^j {n \brack j}_q =0$ for n odd
Mar
9
accepted Number of Plane Oriented Recursive Trees
Mar
9
comment Number of Plane Oriented Recursive Trees
Aaah! Well that makes me feel a lot better, thank you!!
Mar
9
asked Number of Plane Oriented Recursive Trees
Aug
14
asked How to find the period of a recurrence relation
Jul
6
accepted Find order of elliptic curve
Jul
6
asked Find order of elliptic curve
Jun
26
awarded  Yearling
Jun
26
accepted Factor RSA number $n$.
Jun
26
revised Factor RSA number $n$.
edited body
Jun
26
revised Factor RSA number $n$.
edited body
Jun
26
asked Factor RSA number $n$.
Feb
1
awarded  Talkative
Feb
1
comment How to work with a statement: “for all $x$, if $p(x)$ then $q(x)$” (contradiction and contraposition)
Let us continue this discussion in chat.
Feb
1
comment How to work with a statement: “for all $x$, if $p(x)$ then $q(x)$” (contradiction and contraposition)
The tautologies (K.0)-(K.1) on this sheet might be useful to you: math.ethz.ch/~halorenz/4students/logikGT/Tautologien.pdf
Feb
1
comment How to work with a statement: “for all $x$, if $p(x)$ then $q(x)$” (contradiction and contraposition)
No, $\forall x(p(x) \rightarrow q(x))$ is equivalent to $\forall x:(\lnot p(x) \lor q(x))$ That's right, we leave the outer quantifier be.
Feb
1
comment How to work with a statement: “for all $x$, if $p(x)$ then $q(x)$” (contradiction and contraposition)
Because $p \rightarrow q$ is logically equivalent to $\lnot p \lor q$. Since $\lnot q \rightarrow \lnot p$ is the contraposition of $p \rightarrow q$ your statement is equivalent to $\forall x:(\lnot q(x) \rightarrow \lnot p(x))$
Feb
1
awarded  Teacher