Spot the mistake of -1=1 proof
3712
Why $\sqrt{-1 \cdot {-1}} \neq \sqrt{-1}^2$?
154945
$|px^2+qx+r|\le1$ for all $x$ in $[-1; 1]$, show that $|rx^2+qx+p|\le2$ for all $x$ in $[-1; 1]$
81875
why is $\sqrt{-1} = i$ and not $\pm i$?
31783
Is this proof of $ab = 0$ correct?
107765
Prove that there exists two roots in $[-1,1]$
122076
A one line proof that one is zero using Mathematica 10
78736
Check my proof that $(ab)^{-1} = b^{-1} a^{-1}$
97952
Square root of 1 is (not) -1
23883
$\infty = -1 $ paradox
107390
Why is (-1)(-1) = 1?
97890
$\{1,1\}=\{1\}$, origin of this convention
154133
Flawed proof by induction that $a^{n-1}=1$
75387
A proof that $1=2$. May I know why it’s false?
80004
Why is $1/i$ equal to $-i$?
3632
Basic number theory proofs
158862
Show that $a(-1) = (-1)a = -a $.
65923
How to approach proving $f^{-1}(B\setminus C)=A\setminus f^{-1}(C)$?