Explain me why ...

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• Oct 19th 2009, 11:03 AM
SmallMan
Explain me why ...
Can you explain me how this is solved in this way.

f(x, y) = x + 2y + 3.

if x = 3 and y = 1 then f(x, y) = 3 + 2 + 3 = 8. We write f(3, 1) = 8.

I just want to know why x=3 and y=1

HOW ARE THEY SOLVED ?
• Oct 19th 2009, 11:09 AM
Grandad
Hello SmallMan
Quote:

Originally Posted by SmallMan
Can you explain me how this is solved in this way.

f(x, y) = x + 2y + 3.

if x = 3 and y = 1 then f(x, y) = 3 + 2 + 3 = 8. We write f(3, 1) = 8.

I just want to know why x=3 and y=1

HOW ARE THEY SOLVED ?

No reason - this is just an example, that's all. $f(3,1) = 8$.

You might equally well say, when $x = 2$ and $y = 0, f(x,y) = 2+0+3=5$. So $f(2,0) = 5$.

It's just showing you how to use the function notation when it's a function of two variables.

Grandad
• Oct 19th 2009, 11:11 AM
masters
Quote:

Originally Posted by SmallMan
Can you explain me how this is solved in this way.

f(x, y) = x + 2y + 3.

if x = 3 and y = 1 then f(x, y) = 3 + 2 + 3 = 8. We write f(3, 1) = 8.

I just want to know why x=3 and y=1

HOW ARE THEY SOLVED ?

Hi SmallMan,

What is the context of your function? This looks like a min/max function in linear programming. x and y would be determined by the vertices of the feasible region. Is that what this is?

It looks a though x = 3 and y = 1 were given to you up front, and you just substituted them into the function. Can you elaborate a little more?
• Oct 19th 2009, 11:13 AM
SmallMan
Ok i understand. Anyway - i will be inerting here all my question concerning this topic.

Thanks