[RESOLVED]Diff  differential

12052016, 02:30 PM
(This post was last modified: 12082016 02:52 PM by jrozsas.)
Post: #1




[RESOLVED]Diff  differential
Hi,
How can I solve this differential calculation in HP Prime? z= 3x^2  xy +y^2 Considering that (x, y) goes from (2,1) to (1.96,0.95). I've made several attempts, but I can not enter the data correctly. In this other POST (http://www.hpmuseum.org/forum/thread7346.html), something similar happened, but Tim was able to enter the data correctly in LIMIT Leo 

12052016, 09:24 PM
(This post was last modified: 12052016 09:43 PM by Han.)
Post: #2




RE: Diff  differential
Your equation z=3x^2xy+y^2 is not a differential equation. Are there differentials in there that you left out, perhaps?
The diff() command computes the derivative (or partial derivative) of an expression. Usually it takes two parameters: an expression, and a variable of differentiation. For example: diff(x^2*y^3,x) returns 2x*y^3 whereas diff(x^2*y^3,y) returns 3x^2*y^2. If you do not specify a variable, then the default variable 'x' is used. For example, diff(x^2*y^3) returns 2x*y^3. So in your second attempt, it is not clear what you meant by the diff(diff(..)) operation since you did not specify a variable. Did you mean to compute \( \frac{\partial^2}{\partial x^2} (3x^2xy+y^2) \) or did you intend to have something else? In particular, if you have questions on how to use a command, consider using the builtin help: 1) type the command 2) with the cursor on the typed command name, press the help button Usually, the help also provides examples of how to use the commands. For desolve, the help says: Code: Syntax: Graph 3D  QPI  SolveSys 

12062016, 12:03 PM
(This post was last modified: 12062016 12:04 PM by jrozsas.)
Post: #3




RE: Diff  differential
I can not understand. The equation z= 3x^2  xy +y^2 (where(x, y) from (2,1) to (1.96,0.95)) can not be solved with desolve?
Leo 

12062016, 12:26 PM
(This post was last modified: 12062016 12:37 PM by Han.)
Post: #4




RE: Diff  differential
Usually a "derivative" is involved when solving a differential equation. For example, \( y = G_0 \cos(x) + G_1 \sin(x) \) is a general solution to the equation \( \frac{d^2}{dx^2} y(x) + y(x) = 0 \). The equation \( \frac{d^2}{dx^2} y(x) + y(x) = 0 \) can also be written as \( y''(x) + y(x) = 0 \). So in this example, the differential equation \( y''(x) + y(x) = 0 \) involves the second derivative: \( y''(x) \). To solve the equation \( y''(x) + y(x) = 0 \) we use:
desolve(y''(x)+y(x) = 0, y) However, the equation you provided: \( z = 3x^2xy+y^2\) does not involve any (partial) derivative or differential. Google translate: Por lo general, un "derivado" está involucrado cuando se resuelve una ecuación diferencial. Por ejemplo, \(y = G_0 \cos (x) + G_1 \sin (x) \) es una solución general a la ecuación \(\frac {d^2} {dx^2} y (x) + y(x) = 0 \). La ecuación \(\frac {d^2} {dx^2} y (x) + y(x) = 0 \) también se puede escribir como \(y '' (x) + y (x) = 0\). Así, en este ejemplo, la ecuación diferencial \(y '' (x) + y (x) = 0 \) implica la segunda derivada: \(y '' (x) \). Para resolver la ecuación \(y '' (x) + y (x) = 0 \) utilizamos: Desolve (y '' (x) + y (x) = 0, y) Sin embargo, la ecuación que proporcionó: \(z = 3x ^ 2xy + y ^ 2 \) no implica ninguna derivada (parcial) o diferencial. Graph 3D  QPI  SolveSys 

12062016, 12:27 PM
Post: #5




RE: Diff  differential  
12062016, 12:36 PM
Post: #6




RE: Diff  differential
Are you trying to compute:
\[ \int_{1.96}^2 \int_{0.95}^1 \left( 3x^2xy+y^2\right) \ dx\ dy \] Is that what you mean? Graph 3D  QPI  SolveSys 

12062016, 01:41 PM
(This post was last modified: 12062016 01:42 PM by jrozsas.)
Post: #7




RE: Diff  differential
(12062016 12:27 PM)roadrunner Wrote: Leo,Roadrunner, YESSSSSSS!!!!! Great! Thank you all for your help! Leo 

12062016, 01:50 PM
Post: #8




RE: Diff  differential
(12062016 12:36 PM)Han Wrote: Are you trying to compute: No, but roadrunner sent the screen that solved the doubt. Thank you! Leo 

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