Proof by finding a bijection
7083
Alternating sum of binomial coefficients: given $n \in \mathbb N$, prove $\sum^n_{k=0}(-1)^k {n \choose k} = 0$
145447
bilinear form - proof
4610
Proving an identity with a combinatorial proof: $\binom{n}{k}\binom{k}{r}=\binom{n}{r}\binom{n-r}{k-r}$
148731
Constructing a bijection between $[a,b)$ to $(0,1)$
73221
How can I form a bijection between $\mathcal P(A)$ and $2^A$.
27188
Bijection between $\mathbb{R}$ and $\mathbb{R}/\mathbb{Q}$
119549
Prove the even integers are countable (by explicitly giving a bijection $\mathbb{N} \to E$)
44689
Explicit bijection between $[0,1)$ and $(0,1)$
5801
Combinatorial proof help
110569
Does anyone know a closed-form expression for a bijection between $\mathbb{N}^k$ and $\mathbb{N}$?
45792
Rigorous proof that surjectivity implies injectivity for finite sets
74502
Proving the bijection of a continuous function $f$ such that $|f(x)-f(y)| \geq \log(1+|x-y|) \forall x,y$ in $\mathbb{R}.$
113109
Showing that a map is bijective and finding its inverse
24212
proving how many permutations exist.
38257
Continuous bijection from $(0,1)$ to $[0,1]$
128966
Explicit bijection between $\Bbb R$ and permutations of $\Bbb N$
157268
Proving a bijection with absolute value