i. m. soloveichik

 68 Surprising identities / equations 11 If $a^3 b = ba^3$ and if $a$ has order 7, show that $ab = ba$ 11 Books on Number Theory for Layman 10 Proof problem: Show that $n^2-1$ is divisible by $8$, if $n$ is an odd positive integer. 7 Is the following field extension normal $\mathbb Q \sqrt {2+\sqrt 2}\mid \mathbb Q$

### Reputation (3,779)

 +10 In Group theory proofs what is meant by “well defined” +10 The construction of solution of Newton-Pepys problem +6 Need help with inequality -2 How to solve this equation:$\sqrt{x-\sqrt{x-\sqrt{x-\sqrt{x-5}}}}=5$

### Questions (10)

 10 Groups of order $n^2$ that have no subgroup of order $n$ 6 Largest Equilateral Triangle in a Polygon 5 Unique normal subgroups of every possible order 4 Middle binomial coefficient mod 4 4 Another Presentation of Certain Cyclic Groups

### Tags (122)

 58 group-theory × 42 22 elementary-number-theory × 14 58 abstract-algebra × 38 17 finite-groups × 18 30 field-theory × 15 16 calculus × 12 25 galois-theory × 18 15 algebra-precalculus × 18 23 linear-algebra × 13 14 polynomials × 9