### Author Topic: Problem 1  (Read 1857 times)

#### Emily Deibert ##### Problem 1
« on: September 29, 2015, 08:39:18 PM »
1.
http://www.math.toronto.edu/courses/apm346h1/20159/PDE-textbook/Chapter1/S1.P.html#problem-1.P.1
a) Linear homogeneous
b) Nonlinear (quasilinear) homogeneous
c) Linear homogeneous
d) Nonlinear (quasilinear) inhomogeneous
e) Nonlinear homogeneous (though I am not sure, as this one seems like it could also be called inhomogeneous semilinear?) I think I have decided that this one is semilinear. Indeed
f) Nonlinear inhomogeneous
g) Nonlinear inhomogeneous
h) Nonlinear homogeneous Linear homogeneous
i) Nonlinear inhomogeneous
j) Nonlinear homogeneous
« Last Edit: October 03, 2015, 05:02:37 AM by Victor Ivrii »

#### Andrew Lee Chung

• Jr. Member
•  • Posts: 9
• Karma: 0 ##### Re: Problem 1
« Reply #1 on: September 30, 2015, 03:34:51 PM »
e) semi linear is always inhomogeneous?
shouldn't h) be linear homogeneous?

#### Jinghan Cui

• Newbie
• • Posts: 1
• Karma: 0 ##### Re: Problem 1
« Reply #2 on: October 01, 2015, 01:42:44 AM »
If an equation has a variable coefficient, will it also be considered as semilinear? (From chapter 1.3. Classification of equations, it looks like that coefficient as variable also results into a semilinear form.)
\begin{equation} Lu := a_{11}(x,y) u_{xx} + 2a_{12}(x,y) u_{xy} + a_{22}(x,y) u_{yy} = f(x,y,u,u_x,u_y)\end{equation}
Then questions like a) are semilinear homogeneous, which is a subgroup of nonlinear equation?

#### Emily Deibert ##### Re: Problem 1
« Reply #3 on: October 01, 2015, 03:12:50 PM »
Andrew, thank you for pointing out my typo in (h)! It is of course homogeneous.

#### Victor Ivrii ##### Re: Problem 1
« Reply #4 on: October 03, 2015, 05:05:10 AM »
We apply homogeneous/inhomogeneous classification only for linear equations. I corrected in text crossing out homogeneous/inhomogeneous when this is not applicable and typing in red the correct answers when needed