mathematica [Math]

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From: Michael Robinson on 29 Jul 2010 21:15

I have an expression in x and y (an output line). I have values of x and y
for which I need to evaluate the expression. How do I input the values and
command mathematica to evaluate the expression?

From: Michael Robinson on 29 Jul 2010 21:39

From: Michael Robinson on 29 Jul 2010 22:04

"Michael Robinson" <nospam(a)billburg.com> wrote in message
news:0Ip4o.47779$YX3.18857(a)newsfe18.iad...
>I have an expression in x and y (an output line). I have values of x and y
>for which I need to evaluate the expression. How do I input the values and
>command mathematica to evaluate the expression?
>
>
Another problem.
Now mathematica is doing something it shouldn't be doing.
When I put in an expression such as
i = 3 x^2 + 2 y^2 - 4 y + 1

it should just reprint the expression on the next line.

But now it's putting out a numerical expression.

I've tried using the "clear" command for i, also for x and y, but it just
keeps doing it.

From: amzoti on 29 Jul 2010 23:52

On Jul 29, 7:04 pm, "Michael Robinson" <nos...(a)billburg.com> wrote:
> "Michael Robinson" <nos...(a)billburg.com> wrote in message
>
> news:0Ip4o.47779$YX3.18857(a)newsfe18.iad...>I have an expression in x and y (an output line). I have values of x and y
> >for which I need to evaluate the expression. How do I input the values and
> >command mathematica to evaluate the expression?
>
> Another problem.
> Now mathematica is doing something it shouldn't be doing.
> When I put in an expression such as
> i = 3 x^2 + 2 y^2 - 4 y + 1
>
> it should just reprint the expression on the next line.
>
> But now it's putting out a numerical expression.
>
> I've tried using the "clear" command for i, also for x and y, but it just
> keeps doing it.

Perhaps what you want if f[x_, y_] := 3 x^2 + 2 y^2 - 4 y + 1

Now, you want to plug values in for x and y, for example:

x=0, y=0 is f[0,0] (shift-enter)

x = 3, y = 5 is f[3,5] (shift-enter)

x = 3, y = -11 is f[3,-11] (shift-enter)

Note that x and y can be Z or R or Q

Is that what you are looking for?

Recommendation: read the MMA introduction for basic operations - it
will help a lot.

From: amzoti on 29 Jul 2010 23:53

On Jul 29, 6:39 pm, "Michael Robinson" <nos...(a)billburg.com> wrote:
> "Michael Robinson" <nos...(a)billburg.com> wrote in message
>
> news:0Ip4o.47779$YX3.18857(a)newsfe18.iad...>I have an expression in x and y (an output line). I have values of x and y
> >for which I need to evaluate the expression. How do I input the values and
> >command mathematica to evaluate the expression?
>
> What I mean is, how do I plug in values to a symbolic expression?

Can you show what you did?

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