Recent content by iris_m

If you want to prove that a graph isn't planar, you have to prove that it can not be "drawn" such that its edges don't cross, it is not enough to see that the current drawing isn't planar. (Sorry about my English, I don't know the right words..) Also, if anyone wanted to know, the graph...

Oh, the first one isn't bipartite, I got that wrong..

rather urgent :(, isomorphic graphs, planar graph I need help with the following two problems: 1) Is this graph planar? 2) Are these two graphs isomorphic? I don't know what to do with these two problems, and I would be really grateful for all your hits and help. For number 1, I've tried...

I'll write everything from the beginning then, I probably got something wrong. I have to solve the following quasilinear equation: x u_x + y u_y= xy-yu I'm trying to find the general soultion so I do the standard procedure from my textbook: \frac{dx}{x}=\frac{dy}{y}=\frac{du}{y(x-u)}...

(urgent) help with integrals needed I was doing an exercise on quasilinear equations, and have come to the point here I have to solve the following: dy=\frac{du}{x-u}, where u=u(x, y). How do I integrate this? Thank you!

Let X and Y be normed spaces. If X and Y are isometrically isomorphic, then their duals X' and Y' are also isometrically isomorphic. I have no idea what to do with this, please help. :(

In the norm. My justification would be that f_n are continuous functions, so integral and limit commute.

Homework Statement Let X=(C([0,1]), || . ||_1 ), where ||f||_1=\int_{0}^{1}|f(t)|dt. Let M=\{f \in C([0,1]) : \int_{0}^{1}f(t)dt=2, f(1)=0\}. Is M closed in X? The Attempt at a Solution I've tried the following: Let f_n be a sequence in M such that f_n \rightarrow f. I'm checking whether f...