Fake proof : $-1 = \pm 1$
3712
Why $\sqrt{-1 \cdot {-1}} \neq \sqrt{-1}^2$?
55094
How to show $i^{-1} = -i$?
81875
why is $\sqrt{-1} = i$ and not $\pm i$?
145466
Is this a valid mathematical proof?
45171
How prove this $(p-1)!\left(1+\frac{1}{2}+\frac{1}{3}+\cdots+\frac{1}{p-1}\right)\equiv 0\pmod{p^2}$
96398
An integer $a \pmod m$ has inverse if and only if $\gcd(a,m)=1$?
101349
$-1$ isn't a quadratic residue $\pmod{p}, p=4k+3$.
73238
Show that $a^{q-1} \equiv 1 \pmod{pq}$
66089
Using AM-GM to prove $\lim_{p\to 0}$ of the $p$-mean is equal to the GM.
62382
I suppose $(a,m)=(a-1,m)=1$, show that $1+a+a^2+\ldots+a^{\phi(m)-1}\equiv0\pmod m$
111505
Proof $\binom{p-1}{k}\equiv (-1)^k \mod{p}$
83022
Proof of this fairly obscure differentiation trick?
41645
Checking my understanding: $1 - 1 + 1 - 1 + 1 - ... = \frac{1}{2}$
79274
$1=2$ | Continued fraction fallacy
59872
How to prove $\inf(S)=-\sup(-S)$?
154133
Flawed proof by induction that $a^{n-1}=1$
77076
Proof that $(x-1)^2$ divides a $nx^{n+1} – (n+1)x^{n}+1$