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向量方程与张成

向量方程与张成

1. Introduction

Introduction

2. Vector Equations

Vector Equations

3. Spans

Spans

4. What a span looks like

Let v1v_1 and v2v_2 be two noncollinear vectors in R3\mathbb{R}^3. Which of the following is Span⁡{v1,v2}\operatorname{Span}\{v_1,v_2\}?

5. Solving a vector equation

Solve the vector equation

x(12)+y(21)=(54).x\begin{pmatrix}1\\2\end{pmatrix} + y\begin{pmatrix}2\\1\end{pmatrix} = \begin{pmatrix}5\\4\end{pmatrix}.

Which pair (x,y)(x,y) satisfies it?

6. Vocabulary: span

In one word: the collection of all linear combinations of a list of vectors is called the ______ of those vectors.

7. Is $b$ in the span?

Decide whether b=(912)b=\begin{pmatrix}9\\12\end{pmatrix} lies in Span⁡{v,w}\operatorname{Span}\{v,w\} where v=(12)v=\begin{pmatrix}1\\2\end{pmatrix} and w=(45)w=\begin{pmatrix}4\\5\end{pmatrix}, by solving xv+yw=bxv + yw = b. Enter x,yx,y (for example: 1,2).

8. Parameterizing a plane

The plane x−3y−z=12x - 3y - z = 12 passes through (12,0,0)(12,0,0). Every point of the plane can be written as

(xyz)=(1200)+y( ? 10)+z( ? 01).\begin{pmatrix}x\\y\\z\end{pmatrix} = \begin{pmatrix}12\\0\\0\end{pmatrix} + y\begin{pmatrix}\ ?\ \\1\\0\end{pmatrix} + z\begin{pmatrix}\ ?\ \\0\\1\end{pmatrix}.

Solve the equation for xx and enter the first component of the yy-direction vector (a number).

9. When two vectors span the plane

Let v1v_1 and v2v_2 be two vectors in R2\mathbb{R}^2. The equality Span⁡{v1,v2}=R2\operatorname{Span}\{v_1,v_2\} = \mathbb{R}^2 holds under which condition?

10. Read a stretching factor

The vectors (1,2)(1,2) and (2,4)(2,4) span a line through the origin. The point (3,6)(3,6) lies on that line as c⋅(1,2)c\cdot(1,2). Enter the scalar cc.

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