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One-to-one and Onto Transformations

One-to-one and Onto Transformations

1. Introduction

Introduction

2. One-to-one Transformations

One-to-one Transformations

3. Onto Transformations

Onto Transformations

4. Comparison

Comparison

5. One-to-one or onto?

Let

A=(100110)A=\left(\begin{array}{cc} 1 & 0 \\ 0 & 1 \\ 1 & 0 \end{array}\right)

and let T(x)=AxT(x)=Ax, so T ⁣:R2→R3T\colon\mathbb{R}^2\to\mathbb{R}^3. Which statement is correct?

6. A wide matrix of full rank

A 3×53\times 5 matrix AA has rank 33. What can you say about the transformation T(x)=AxT(x)=Ax?

7. Vocabulary: onto

In one word: a transformation T ⁣:Rn→RmT\colon\mathbb{R}^n\to\mathbb{R}^m is ______ if for every vector bb in Rm\mathbb{R}^m the equation T(x)=bT(x)=b has at least one solution.

8. Dimension of the range

Let

A=(123246)A=\left(\begin{array}{ccc} 1 & 2 & 3 \\ 2 & 4 & 6 \end{array}\right)

and let T(x)=AxT(x)=Ax. Enter the dimension of the range of TT (a number).

9. Null space of a full-row-rank matrix

Let

A=(120100013000001),A=\left(\begin{array}{ccccc} 1 & 2 & 0 & 1 & 0 \\ 0 & 0 & 1 & 3 & 0 \\ 0 & 0 & 0 & 0 & 1 \end{array}\right),

so that T(x)=AxT(x)=Ax maps R5\mathbb{R}^5 to R3\mathbb{R}^3. Enter the dimension of the null space of AA (a number).

10. One-to-one via the null space

For the matrix transformation T(x)=AxT(x) = Ax, the transformation is one-to-one exactly when which condition holds?

11. Free variables from the shape

A 2×32\times 3 matrix AA has columns that span R2\mathbb{R}^2. How many free variables does Ax=0Ax = 0 have?

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