### 数学代写|图论作业代写Graph Theory代考| Color the graph below on the right

statistics-lab™ 为您的留学生涯保驾护航 在代写图论Graph Theory方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写图论Graph Theory代写方面经验极为丰富，各种代写图论Graph Theory相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 数学代写|图论作业代写Graph Theory代考|EXERCISES

Color the graph below on the right by reversing the longer section of the two sections of the G-Y Kempe chains from the left graph. Does the coloring of the new graph still satisfy the four-color theorem? Are there any sections of Kempe chains ( $B-G, B-R, B-Y, G-R, G-Y$, or $R-Y$ ) that can’t be reversed in the new graph without causing the new coloring to no longer satisfy the four-color theorem? If so, which sections of which chains? If the coloring of a graph satisfies the four-color theorem and sections of Kempe chains are reversed one at a time, will the new coloring always satisfy the four-color theorem?

The graph below shows a vertex with degree four and two Kempe chains. There are other vertices and edges which aren’t shown. If either Kempe chain A-B or C-D is reversed, E is still surrounded by 4 colors. How can a graph like this can satisfy the four-color theorem?Challenge problem 1: Every MPG is triangulated, meaning that each edge is shared by two triangles. For any MPG, if you choose any of its faces and two other faces that each shares an edge with the first face, you will obtain a structure like that shown below. The partial graph below shows face BCE and two other faces (ABE and CDE) that share an edge with it. (The third face that shares an edge with BCE is not shown. There are also many other vertices and edges in the MPG that are not shown.) Apply Kempe chains to prove that, regardless of what the rest of the MPG looks like, the five vertices shown below can always be colored using no more than four different colors. Since we may apply this argument to any face in any MPG and two of that face’s neighboring faces, does this prove the four-color theorem? Explain.

(Note how this differs from Kempe’s argument for a vertex with degree five – even though every vertex in the diagram above may be degree five or higher – in that there isn’t a central vertex connecting to all five of these vertices. We only need to color the five vertices shown above using four colors, whereas in Kempe’s argument for a vertex with degree five we need to color the five surrounding vertices using three colors. This problem is simpler than Kempe’s problem of the vertex with degree five, since we only need to recolor a single vertex.)

Note: The answer key doesn’t include answers to the challenge problems. These problems are intended to encourage you to think about the ideas.

## 数学代写|图论作业代写Graph Theory代考|The partial graph for a MPG

Challenge problem 2: The partial graph for a MPG below shows vertices $X$ and $Y$ with degree five. There are also many other vertices and edges in the MPG that are not shown. Can you apply the concept of Kempe chains to prove that $\mathrm{X}$ and $\mathrm{Y}$ can always be chosen so that both vertices are always four-colorable? Either prove this, or explain why this is impossible or very difficult. Could this proof (if it can be done) be used to prove the four-color theorem? Explain. (The main idea is this: Can you apply Kempe chains to A thru F so that $\mathrm{X}$ and $\mathrm{Y}$ are always four-colorable?)

Note that if you chain A to D and chain A to E, you can reverse F, but don’t need to worry about reversing $Y$ (at least for the first part of the problem, it is free to be chosen as desired).

You should also not only consider the possibility of using Kempe chains to force two vertices connected to either $\mathrm{X}$ or $\mathrm{Y}$ to be different, but should also consider the possibility of using Kempe chains to force one vertex connected to $\mathrm{X}$ and another vertex connected to $\mathrm{Y}$ to be the same color. For example, connecting $\mathrm{B}$ to $\mathrm{F}$ and $\mathrm{C}$ to $\mathrm{E}$, you can force two neighbors of $X$ to be the same colors as two neighbors of $Y$. (Note that there is also the special case where one or both of $\mathrm{E}$ and $\mathrm{F}$ could be the same vertex as B or C, for example.) Note: The answer key doesn’t include answers to the challenge problems. These problems are intended to encourage you to think about the ideas. Challenge problem 3: The MPG below is “nearly four-colored.” One vertex has a fifth color, X. If the edge connecting the two shaded vertices is contracted (see Chapter 6), the graph would then be properly four-colored.

Show that $\mathrm{X}$ can be moved down to the left onto the vertex currently colored Y by reversing the colors of one section of a Kempe chain, allowing the graph to be four-colored. If we try to move $\mathrm{X}$ to the left onto the vertex currently colored $\mathrm{G}$, the analogous color reversal poses a problem. Explain. Is it possible to move $\mathrm{X}$ onto any desired vertex in the entire MPG? Can you prove that such a “nearly four-colored” MPG can always be four-colored by moving $X$ onto a new vertex? Can you use this to prove the four-color theorem?

Note: The answer key doesn’t include answers to the challenge problems. These problems are intended to encourage you to think about the ideas. You may wish to review your ideas for this solution when you read about VS3 in Chapter $18 .$

## 数学代写|图论作业代写Graph Theory代考|A FEW NOTABLE

The triangle graph has 3 vertices and 3 edges. The triangle graph has the fewest vertices of any MPG, is three-colorable, and its edges make a single complete cycle (a closed chain). It is both a cycle graph (with its edges forming a closed chain) and a complete graph (every vertex connects to all of the other vertices), which is why it may be called $\mathrm{C}{3}$ or $\mathrm{K}{3}$.

The tetrahedral graph has 4 vertices and 6 edges. The tetrahedral graph has the most vertices that a complete graph can have and also be a MPG, and has the most vertices that a complete graph can have and be four-colored.

A pentahedral MPG has 5 vertices and 9 edges. It is the dual of the square pyramid. Recall from Chapter 4 that the dual representation swaps the roles of the vertices and faces between graphs and maps (see the solution to Problem 1 in Chapter 4). If you add edge $\mathrm{AC}$ to the pentahedral graph shown below, it would become the complete graph $\mathrm{K}_{5}$.

There are two structurally different hexahedral MPG’s which have 6 vertices and 12 edges. One of these is the octahedral MPG. (Here, the prefix “octa,” meaning 8, refers to the faces, not the vertices. An octahedron is a polyhedron formed by joining two square pyramids at their square base, such that it has 6 vertices, 12 edges, and 8 triangular faces. It is the dual polyhedron to the cube, which has 8 vertices, 12 edges, and 6 faces. See the solution to Problem 1 in Chapter 4.) The octahedral MPG is the only MPG where every vertex has degree 4 . The other hexahedral MPG has two vertices with degree 5 , two with degree 4 , and two with degree 3 . (In the case of hexahedral, the prefix “hexa” indicates 6 vertices, and includes the octahedral graph.)

## 数学代写|图论作业代写Graph Theory代考|EXERCISES

（请注意，这与 Kempe 的关于五度顶点的论点有何不同——即使上图中的每个顶点都可能是五度或更高——因为没有一个中心顶点连接到所有五个顶点。我们只需要用四种颜色为上面显示的五个顶点着色，而在 Kempe 的五度顶点论证中，我们需要使用三种颜色为周围的五个顶点着色。这个问题比 Kempe 的五度顶点问题更简单，因为我们只需要重新着色单个顶点。）

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## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

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The graphs above are incomplete. These figures only show a vertex with degree four (vertex E), its nearest neighbors (A, B, C, and D), and segments of A-C Kempe chains. The entire graphs would also contain several other vertices (especially, more colored the same as B or D) and enough edges to be MPG’s. The left figure has A connected to $C$ in a single section of an A-C Kempe chain (meaning that the vertices of this chain are colored the same as A and C). The left figure shows that this A-C Kempe chain prevents B from connecting to $\mathrm{D}$ with a single section of a B-D Kempe chain. The middle figure has A and C in separate sections of A-C Kempe chains. In this case, B could connect to D with a single section of a B-D Kempe chain. However, since the A and C of the vertex with degree four lie on separate sections, the color of C’s chain can be reversed so that in the vertex with degree four, C is effectively recolored to match A’s color, as shown in the right figure. Similarly, D’s section could be reversed in the left figure so that D is effectively recolored to match B’s color.

Kempe also attempted to demonstrate that vertices with degree five are fourcolorable in his attempt to prove the four-color theorem [Ref. 2], but his argument for vertices with degree five was shown by Heawood in 1890 to be insufficient [Ref. 3]. Let’s explore what happens if we attempt to apply our reasoning for vertices with degree four to a vertex with degree five.

## 数学代写|图论作业代写Graph Theory代考|The previous diagrams

The previous diagrams show that when the two color reversals are performed one at a time in the crossed-chain graph, the first color reversal may break the other chain, allowing the second color reversal to affect the colors of one of F’s neighbors. When we performed the $2-4$ reversal to change B from 2 to 4 , this broke the 1-4 chain. When we then performed the 2-3 reversal to change E from 3, this caused C to change from 3 to 2 . As a result, F remains connected to four different colors; this wasn’t reversed to three as expected.
Unfortunately, you can’t perform both reversals “at the same time” for the following reason. Let’s attempt to perform both reversals “at the same time.” In this crossed-chain diagram, when we swap 2 and 4 on B’s side of the 1-3 chain, one of the 4’s in the 1-4 chain may change into a 2, and when we swap 2 and 3 on E’s side of the 1-4 chain, one of the 3’s in the 1-3 chain may change into a 2 . This is shown in the following figure: one 2 in each chain is shaded gray. Recall that these figures are incomplete; they focus on one vertex (F), its neighbors (A thru E), and Kempe chains. Other vertices and edges are not shown.

Note how one of the 3’s changed into 2 on the left. This can happen when we reverse $\mathrm{C}$ and $\mathrm{E}$ (which were originally 3 and 2 ) on E’s side of the 1-4 chain. Note also how one of the 4’s changed into 2 on the right. This can happen when we reverse B and D (which were originally 2 and 4) outside of the 1-3 chain. Now we see where a problem can occur when attempting to swap the colors of two chains at the same time. If these two 2’s happen to be connected by an edge like the dashed edge shown above, if we perform the double reversal at the same time, this causes two vertices of the same color to share an edge, which isn’t allowed. We’ll revisit Kempe’s strategy for coloring a vertex with degree five in Chapter $25 .$

## 数学代写|图论作业代写Graph Theory代考|The shading of one section of the B-R

• MPG 是三角测量的。它由具有三个边和三个顶点的面组成。
• 每个面的三个顶点必须是三种不同的颜色。
• 每条边由两个相邻的三角形共享，形成一个四边形。
• 每个四边形将有 3 或 4 种不同的颜色。如果与共享边相对的两个顶点恰好是相同的颜色，则它有 3 种颜色。
• 对于每个四边形，四个顶点中的至少 1 个顶点和最多 3 个顶点具有任何颜色对的颜色。例如，具有 R、G、B 和G有 1 个顶点R−是和3个顶点乙−G，或者您可以将其视为 1 个顶点乙−是和3个顶点G−R，或者您可以将其视为 BR 的 2 个顶点和 GY 的 2 个顶点。在后一种情况下，2G’ 不是同一链的连续颜色。
• 当您将更多三角形组合在一起（四边形仅组合两个）并考虑可能的颜色时，您将看到 Kempe 的部分

• 画一张R顶点和一个是由边连接的顶点。
• 如果一个新顶点连接到这些顶点中的每一个，它必须是乙或者G.
• 如果一个新顶点连接到 R 而不是是，可能是是,乙， 或者G.
• 如果一个新的顶点连接到是但不是R，可能是R,乙， 或者G.
• RY 链要么继续增长，要么被 B 包围，G.
• 如果你关注 B 和 G，你会为它的链条得出类似的结论。
• 如果一条链条完全被其对应物包围，则链条的新部分可能会出现在其对应物的另一侧。
Kempe 证明了所有具有四阶的顶点（那些恰好连接到其他四个顶点的顶点）都是四色的 [Ref. 2]。例如，考虑下面的中心顶点。

## 数学代写|图论作业代写Graph Theory代考|In the previous figure

• A 和 C 或者是 AC Kempe 链的同一部分的一部分，或者它们各自位于 AC Kempe 链的不同部分。（如果一种和C例如，是红色和黄色的，则 AC 链是红黄色链。） – 如果一种和C每个位于 AC Kempe 链的不同部分，其中一个部分的颜色可以反转，这有效地重新着色 C 以匹配 A 的颜色。如果 A 和 C 是 AC Kempe 链的同一部分的一部分，则 B 和 D每个都必须位于 BD Kempe 链的不同部分，因为 AC Kempe 链将阻止任何 BD Kempe 链从 B 到达 D。（如果乙和D是蓝色和绿色，例如，那么一种BD Kempe 链是蓝绿色链。）在这种情况下，由于 B 和 D 分别位于 BD Kempe 链的不同部分，因此 BD Kempe 链的其中一个部分的颜色可以反转，这有效地重新着色 D 以匹配 B颜色。– 因此，可以使 C 与 A 具有相同的颜色或使 D 具有与 A 相同的颜色乙通过反转 Kempe 链的分离部分。

Kempe 还试图证明五阶顶点是可四色的，以证明四色定理 [Ref. 2]，但 Heawood 在 1890 年证明他关于五次顶点的论点是不充分的 [Ref. 3]。让我们探讨一下如果我们尝试将我们对度数为四的顶点的推理应用于度数为五的顶点会发生什么。

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。