Newbetuts

Prove that for every three non-zero integers, a,b and c, at least one of the three products ab,ac,bc is positive

How to prove P(A ∪ B) = P(A) + P(B|A′)P(A′)?

Does $\left\{\frac{p^a}{q^b}:p,q\in\mathbb{Z}\right\}=\left\{\frac{j^{\gcd(a,b)}}{k^{\gcd(a,b)}}:j,k\in\mathbb{Z}\right\}$ for $a,b\in\mathbb{N}$?

is it allowed to have nesting Induction?

Prove that $\{x_1=1,\,x_{n+1}=\frac {x_n}2+\frac 1{x_n} \}$ converges when $n \to \infty$

Use the division algorithm to prove that 3|(n³ + 2n) for all n ∈ ℕ

Is this proof correct? $2^\sqrt{2 \log n} \in Ω(\log^2n)$.

Proving that if $a,b$ are even, then $\gcd(a,b) = 2 \gcd(a/2, b/2)$ [duplicate]

Proof of a summation of $k^4$

If $ar + bs =1$, then $\gcd(a,s) = \gcd(r,b) = \gcd(r,s) = 1$ [duplicate]

Proving $11$ never divides $64^n +22^n -2$

Hint in Proving that $n^2\le n!$ [duplicate]

Is this Theorem equivalent to Axiom of Choice?

Proof of the irrationality of $\sqrt{3}$ - logic question

Is this direct proof of an inequality wrong?

Solving two simultaneous recurrence relations

Proof there is a rational between any two reals

New posts in proof-writing

How do we know all numbers alternate between odd and even numbers?

Orthogonal set and linear independence and proofs.

formal proof from calulus

Prove that for every three non-zero integers, a,b and c, at least one of the three products ab,ac,bc is positive

How to prove P(A ∪ B) = P(A) + P(B|A′)P(A′)?

Does $\left\{\frac{p^a}{q^b}:p,q\in\mathbb{Z}\right\}=\left\{\frac{j^{\gcd(a,b)}}{k^{\gcd(a,b)}}:j,k\in\mathbb{Z}\right\}$ for $a,b\in\mathbb{N}$?

is it allowed to have nesting Induction?

Prove that $\{x_1=1,\,x_{n+1}=\frac {x_n}2+\frac 1{x_n} \}$ converges when $n \to \infty$

Use the division algorithm to prove that 3|(n³ + 2n) for all n ∈ ℕ

Is this proof correct? $2^\sqrt{2 \log n} \in Ω(\log^2n)$.

Proving that if $a,b$ are even, then $\gcd(a,b) = 2 \gcd(a/2, b/2)$ [duplicate]

Proof of a summation of $k^4$

If $ar + bs =1$, then $\gcd(a,s) = \gcd(r,b) = \gcd(r,s) = 1$ [duplicate]

Proving $11$ never divides $64^n +22^n -2$

Hint in Proving that $n^2\le n!$ [duplicate]

Is this Theorem equivalent to Axiom of Choice?

Proof of the irrationality of $\sqrt{3}$ - logic question

Is this direct proof of an inequality wrong?

Solving two simultaneous recurrence relations

Proof there is a rational between any two reals