real value

**omega360** · Apr6-09, 12:53 AM

i'm not sure whether this is the right place to post this but i need to know what a real value of an expression is. also can any one tell how i could find the least possible real value of an expression.

**CRGreathouse** · Apr6-09, 01:48 AM

Originally Posted by omega360

also can any one tell how i could find the least possible real value of an expression.

Without context, how could we know how to answer this?

My best guess would be "take the derivative, set it equal to zero, and check each occurrence". There are less advanced answers (for those who don't know calculus yet) and more advanced answers (Richardson's theorem says if the expression is sufficiently (not very!) complicated, it's undecidable in general).

**omega360** · Apr6-09, 03:42 AM

could you tell me how to find the least possible real value of this expression:(where n is a real number)
(n squared) minus (3n) plus [the square root of (n – 3)] minus [the square root of (n – 3)]

**matt grime** · Apr6-09, 04:59 AM

$LaTeX Code: n^2 - 3n + \\sqrt{n-3} - \\sqrt{n-3}$

is what you wrote, and the last two terms cancel so it probably wasn't what you wanted.

**CRGreathouse** · Apr6-09, 01:05 PM

Well, that would make it easy to find the minimum...

**AUMathTutor** · Apr6-09, 01:57 PM

Agreed. Just to make sure we're on the same page, the answer would be

n=3/2, val=-9/4

True story?