System of linear equations For $A \in \mathbf{F}^{m\times n}$ and one particular $b \in \mathbf{F}^n$, then $Ax = b$ has exactly one solution $\iff$ ($ A $ injective) and ($ b \in \operatorn...

Invariant Subspaces Null space and range of $ p(T) $ are invariant under $ T $. Suppose $ T \in \mathcal{L}(V) $ and $ U $ is a subspace of $ V $ invariant under $ T $. Then $ U $ is invar...

Polynomials Bézout identity Suppose $ p, q \in \mathcal{P}(\mathbf{C}) $ are nonconstant polynomials with no zeros in common. Let $ m = \deg p $ and $ n = \deg q $. There exist $ r \in \math...

Dual Space and Dual Map Suppose $V$ is finite-dimensional. Then $ V \cong V’ $, but finding an isomorphism from $V$ onto $V’$ generally requires choosing a basis of $V$. $ \dim U^0 ...

Extension and Lift: A Factoring Duality Extension (shared domain) Suppose $ W_1 $ is finite-dimensional, $ S \in \mathcal{L}(V, W_1) $ and $ T \in \mathcal{L}(V, W_2) $. Then \(\operatorname...

Affine subspace affine = linear structure with the origin forgotten An operation on points commutes with every translation $ x \mapsto x + t $ if and only if its coefficients sum to 1. ...

3E 11. Suppose $ U = \{ (x1,x2,\dots) \in \mathbf{F}^\infty : x_k \ne 0 \ \text{for only finitely many k} \} $. (b) Prove that $ \mathbf{F}^\infty/U $ is infinite-dimensional. Goal and str...

Vector Space Definition Motivation: properties of addition and scalar multiplication in $ \mathbf{F}^n $ flowchart LR subgraph addGroup["$$u + v$$"] direction TB addSet["abelian group under...

一、期权的本质 期权是一份合约，赋予买方在特定时间内、以特定价格买入或卖出某资产的权利，但没有义务。 持有期权 ≠ 持有股权。持有股票意味着拥有公司所有权（可投票、收股息）；持有期权只是拥有未来买卖股票的权利，行权前什么都不拥有。 期权的核心不对称性：买方权利无义务，卖方义务无权利。 二、四个核心要素 要素 说明 ...

一、债券基础 债券（Bond）是借条的标准化版本：借款方（发行人）向投资者借钱，承诺定期支付利息，到期归还本金。持有人是债主，不是股东。 核心要素 要素 英文 含义 面值 Face Value / Par Value 到期归还的本金，通常 $1000 ...