Linear Algebra: Range and Null Space

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6 Questions

What is the set of all vectors in $\mathbb{R}^{m}$ that can be written as linear combinations of the columns of $A$?

$R(A)$

Which of the following statements is true about the rank of matrix $A$?

The rank is denoted by $r$ and $r \leq \min(m, n)$.

If $A \in \mathbb{R}^{m \times n}$, what is the relationship between $N(A)$ and $\mathbb{R}^{n}$?

$N(A)$ is a subset of $\mathbb{R}^{n}$.

Which of the following correctly describes $N(A)$?

It is the set of all vectors $x \in \mathbb{R}^{n}$ such that $Ax = 0$.

If $A \in \mathbb{R}^{m \times n}$ and its transpose $A^T \in \mathbb{R}^{n \times m}$, what is $R(A^T)$?

The span of the columns of $A^T$.

According to the property $\dim(N(A)) + \dim(R(A)) = n$, what does this imply?

The dimension of the null space and range space of $A$ add up to $n$.

Study Notes

Range Space, R(A)

  • The range space of a matrix A is the set of all vectors in R^m that can be written as linear combinations of the columns of A.
  • Formally, R(A) = span({a_1, a_2,..., a_n}) = {y = Ax, x ∈ R^n, y ∈ R^m}
  • Similarly, R(A^T) = span({a_1, a_2,..., a_m}) = {w = A^Tz, z ∈ R^m, w ∈ R^n}

Properties of Range Space

  • R(A) ⊂ R^m
  • dim(R(A)) or dim(R(A^T)) is the rank of A, denoted by r, and r ≤ min(m, n)

Null Space, N(A)

  • The null space of a matrix A is the set of all vectors x mapped into zero by A.
  • N(A) = {x: Ax = 0, x ∈ R^n}
  • Similarly, N(A^T) = {z: Az = 0, z ∈ R^m}

Properties of Null Space

  • N(A) ⊂ R^n
  • dim(N(A)) + dim(R(A)) = n

This quiz covers the concepts of range and null space in linear algebra, including the definition of range space, null space, and their properties. It's a crucial topic in understanding linear transformations and vector spaces.

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