graph theory

[shahar]

This photo needs to show why K(5) isn't planar?

1. What the meaning that K(5) isn't planar?
2. What is the symbol of K(5) means?
The photo is made with my translation of the explanation.

 

[Dr.Peterson]

I would hope that you found this in a context where "planar graph" was defined, and where K(5) was defined. Can you tell us something about the context?

A picture alone can't "show why K(5) isn't planar", since that is a negative statement; what they say might be the start of a proof of that statement.

For a definition of "planar", see https://en.wikipedia.org/wiki/Planar_graph .

That also contains a link explaining what K(5), or K₅, means.

 

[shahar]

I would hope that you found this in a context where "planar graph" was defined, and where K(5) was defined. Can you tell us something about the context?

A picture alone can't "show why K(5) isn't planar", since that is a negative statement; what they say might be the start of a proof of that statement.

For a definition of "planar", see https://en.wikipedia.org/wiki/Planar_graph .

That also contains a link explaining what K(5), or K₅, means.

Yes, you're right.
There is a contradiction that K(5) isn't planar graph.
When I try to read on Wikipedia, I get stuck on the sentence:

What the meaning of the sentence ?

And I try to look at the presentation that the sentence came from to clarify the contradiction.

 

[Dr.Peterson]

Yes, you're right.
There is a contradiction that K(5) isn't planar graph.
When I try to read on Wikipedia, I get stuck on the sentence:
View attachment 22924
What the meaning of the sentence ?

And I try to look at the presentation that the sentence came from to clarify the contradiction.

That sentence is a definition of "subdivision". If you click on that word, you'll see a fuller definition with examples. That ought to be enough to make it clear.