2
votes
2answers
160 views

Prove that for any give sequence of digits, there is a perfect square starting with that sequence

Prove that for any give sequence of digits, there is a perfect square starting with that sequence. With more details, prove that for $\forall a\in \mathbb{N}$, such that ...
0
votes
1answer
34 views

Approximation of reals by rationals

Is this fact true: For all real $\alpha$, and natural numbers $n$, there exists some $a, q$ with $n^{2/3} \le q \le n$ and $(a, q) = 1$ such that $\left\lvert\alpha - \frac{a}{q}\right\rvert \le ...
2
votes
0answers
46 views

Improving a diophantine approximation

Let $x\in \mathbb T^d=\mathbb R^d/\mathbb Z^d$ and $p/q\in\mathbb Q^d/\mathbb Z^d$ be such that $\|x-p/q\| \leqslant t$ (with $t$ small) and $q\leqslant Q$ can I say that for all $m\in\mathbb N^\star$ ...
2
votes
2answers
86 views

Criteria for irrationality of real numbers

Concerning the criteria for irrationality: Theorem says "A number $\alpha$ is irrational if and only if for every $\epsilon >0$ there exist integers $h$ and $q$ such that $0 < | q\alpha - h | ...
13
votes
5answers
3k views

Fermat's Last Theorem near misses?

I've recently seen a video of Numberphille channel on Youtube about Fermat's Last Theorem. It talks about how there is a given "solution" for the Fermat's Last Theorem for $n>2$ in the animated ...
6
votes
1answer
231 views

Cube roots don't sum up to integer

My question looks quite obvious, but I'm looking for a strict proof for this. (At least, I assume it's true what I claim.) Why can't the sum of two cube roots of positive non-perfect cubes be an ...
2
votes
3answers
167 views

Sum of roots is integer

My question looks quite obvious, but I'm looking for a strict proof for this: Why can't the sum of two square roots of non-perfect squares be an integer? For example: $\sqrt8+\sqrt{15}$ isn't an ...
2
votes
1answer
42 views

Diophantine approximation problem

Denote $||x||=Min(x-[x],1-(x-[x]))$,it means the minimum distance between x and an integer. Can we find a fast algorithm to get a natural number $n$ that satisfies $$||na||<p,||nb||<p,...$$ ...
2
votes
0answers
70 views

How accurately can a irrational algebraic number represent a different irrational number compared to a rational approximation?

If I am trying to approximate $x = \sqrt D$ such that D is a square free integer I can use Diophantine approximation and the Fundamental Recurrence Formulas to find a rational approximation ...
1
vote
1answer
103 views

prove existence of integers $a,q$ which satisfy the following inequality

Let $x \in \mathbb{R}$ and integer $Q \geq 1$. Prove: there exist integers $a$ and $1 \leq q \leq Q$ such that $|x - \frac aq | < \frac 1{qQ} $ any help would be appreciated!
1
vote
2answers
130 views

Constructive proof need to know the solutions of the equations

Observe the following equations: $2x^2 + 1 = 3^n$ has two solutions $(1, 1) ~\text{and}~ (2, 2)$ $x^2 + 1 = 2 \cdot 5^n$ has two solutions $(3, 1) ~\text{and}~ (7, 2)$ $7x^2 + 11= 2 \cdot 3^n$ has ...
3
votes
2answers
189 views

Solutions of $x^2 + 119 = 15 \cdot 2^n$ without trial and error

I seen this equation at math.stack exchange The equation $x^2 + 119 = 15 \cdot 2^n$ has only six solutions. Those are (1,3) (11, 4), (19, 5), (29, 6), (61, 8) and other one is I don't know. This ...
1
vote
2answers
383 views

Solutions of some Diophantine equations

Respected Mathematicians, The diophantine equation $2^x$ + $5^y$ = $z^2$ has solutions $x = 3, y = 0, z = 3$ and $x = 2, y = 1, z = 3$. I got these solutions by trial and error method. To be honest, ...