Prove that $-(-x) = x$ for all real numbers x
37723
Proof that $-(-x) = x$ using just the field axioms
33786
Proof that a certain fraction is always an integer
22232
Proving that cardinality of the reals = cardinality of $[0,1]$
3390
finding the real values of $x$ such that : $x=\sqrt{2+\sqrt{2-\sqrt{2+x}}}$
116056
Prove that $|f(x)-f(y)|\le|x-y|$ for all $x$ and $y$.
22087
Find all real numbers x such that $ |5x-1| ≤ |3x-2|$
108382
Prove $x^n-1$ is divisible by $x-1$ by induction
77076
Proof that $(x-1)^2$ divides a $nx^{n+1} – (n+1)x^{n}+1$
25788
Prove that $i^i$ is a real number
36906
Prove that $x^n+x^{-n} \in \mathbf{N}$ if $x+\frac1x \in \mathbf{N}$
2072
Demonstrate that if $f$ is surjective then $X = f(f^{-1}(X))$
80009
Prove that $| |a|-|b| | \le |a-b|$
110826
prove that : $ i = \sqrt {-1}\ $
3820
Prove that $||x|-|y||\le |x-y|$
116009
Proving that if a set is both open and closed then it is equal to the real numbers
108704
Help with proof of $|x+y| \geq |x|-|y|$
118873
Prove that $f(x)=0$ for all $x\in\mathbb{R}$.