Multiplicative Inverse in $S=\{a+b\sqrt{2} \mid a,b \in \mathbb Q\}$
42332
Existence of multiplicative inverse in field $\mathbb{Q}(\sqrt{d})$
67208
Can we say that there exist an integer $n$ such $A+nB$ invertible?
75639
Showing that $\sqrt[3]{2}\notin\Bbb Q(\alpha_1,...,\alpha_k)$ where $\alpha_i^2\in\Bbb Q\ \forall i$
114506
Expansion of $(1+\sqrt{2})^n$
97303
Calculate the multiplicative inverse modulo a composite number
53660
Show that $ a，b，c, \sqrt{a}+ \sqrt{b}+\sqrt{c} \in\mathbb Q  \implies  \sqrt{a},\sqrt{b},\sqrt{c} \in\mathbb Q $
148946
If $\mathbf{A}$ is a $2\times 2$ matrix that satisfies $\mathbf{A}^2 - 4\mathbf{A} - 7\mathbf{I} = \mathbf{0}$, then $\mathbf{A}$ is invertible
87289
Find the multiplicative inverses of all the elements in $\Bbb Z_{16}^\times$
134619
Galois extension with $X^4-2aX^2+b\in\mathbb Q[X]$
138279
Multiplicative order and powers
141909
Prove ${2}^{n}\cdot(2m+1)-1 $ is invertible
122083
Prove that $\sqrt[3]{2} +\sqrt{5}$ is algebraic over $\mathbb Q$
99037
Prove the sum of all numbers that do not have a multiplicative inverse mod $n$
46831
Show that $ a，b, \sqrt{a}+ \sqrt{b} \in\mathbb Q \implies \sqrt{a},\sqrt{b} \in\mathbb Q $
58133
${a^2}{\mid}({b^3} + 1)\;$and$\;{b^2}{\mid}({a^3} + 1)$
69721
$(a,b) \mathbin\# (c,d)=(a+c,b+d)$ and $(a,b) \mathbin\&(c,d)=(ac-bd(r^2+s^2), ad+bc+2rbd)$. Multiplicative inverse?
53857
Showing $\sup \{ \sin n \mid n\in \mathbb N \} =1$