New posts in Proof Writing

Show that a certain set of invertible matrices is a normal subgroup of another set of invertible matrices (triangular)

Proof $\sum_{k=0}^\infty \binom{k}{n-k} = f_{n+1}$ where $f_n$ is the n-th Fibonacci-number

Can a proof be just words?

Prove that $\frac{k^7}{7}+\frac{k^5}{5}+\frac{2k^3}{3}-\frac{k}{105}$ is an integer.

Is it legitimate to specify a statement as a Theorem if it is proved using numerical methods (since it can't be proved analytically)?

If $f \circ f = 0 $, show that transformations $f + id_x$ and $f - id_x$ are isomorphisms of $X$

Proving set identities: empty set case.

Proof that $\cos(2\theta) = \cos^2\theta-\sin^2\theta$ by showing equivalence of derivatives

What is an example of a proof by minimal counterexample?

How can you prove that $1.05^{50} < 100$ without a calculator?