Date: Jan 14, 2013 12:00 AM
Author: Bob Hanlon
Subject: Re: NSolve output
$Version

"9.0 for Mac OS X x86 (64-bit) (November 20, 2012)"

a = x z + 2 x y + 2 y z;

v = x y z;

a2 = a /. x -> 2 z;

v2 = v /. x -> 2 z;

NSolve[{a2 == 60, v2 == 40, x == 2 z, x > 0},

{x, y, z}]

{{x -> 5.1156, y -> 3.05701, z -> 2.5578}, {x -> 7.46083,

y -> 1.43719, z -> 3.73042}}

Solve[{a2 == 60, v2 == 40, x == 2 z, x > 0},

{x, y, z}, Reals] // N

{{x -> 5.1156, y -> 3.05701, z -> 2.5578}, {x -> 7.46083,

y -> 1.43719, z -> 3.73042}}

{Reduce[{a2 == 60, v2 == 40, x == 2 z, x > 0},

{x, y, z},

Backsubstitution -> True] // N // ToRules}

{{x -> 5.1156, y -> 3.05701, z -> 2.5578}, {x -> 7.46083,

y -> 1.43719, z -> 3.73042}}

Bob Hanlon

On Sat, Jan 12, 2013 at 9:53 PM, Berthold Hamburger

<b-hamburger@artinso.com> wrote:

> Hello,

>

> I want to solve two simple equations with NSOLVE to calculate the

> dimensions of a rectangular box that is open on top. The length of the

> box is twice the width and the volume and area of the box are

> respectively 40 cubic feet and 60 square feet.

>

> I defined the area and volume:

> a = xz + 2xy + 2yz

> v = xyz

>

> then substituted x with 2z:

>

> a2 = a /. x->2z

> v2 = v /. x->2z

>

>

>

> a2 = 6 y z + 2 z^2

> v2 = 2 y z^2

>

> solved with NSolve:

> step1 = NSolve[{a2 == 60, v2 == 40}, {y, z}, Reals] [[1,2]] //Column

>

> which returns the results

> {y->3.05701,z->2.5578}

>

> I would like to get an output that returns values for all 3 variables

> x,y,z as in

>

> {x->5.1156,y->3.05701,z->2.5578}

>

> but somehow cannot find a way to do it

>

> What would be the correct way for doing that?

>

> Regards

>

> Berthold Hamburger

>