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Expert: - 12/14/2007


Question
finding the domain of a function for instance f(x)=the squareroot of x-8

Answer
Questioner:   Alisha
Category:  Advanced Math
Private:  No
 
Subject:  algebra
Question:  finding the domain of a function for instance f(x)=the squareroot of x-8
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Hi, Alesha,

Your basic scheme is:
The domain is all x except the bad ones.  What's a bad one?  An x that makes:

1. A denominator zero.

2. A radicand negative in a square root.

That's what you have here.  The radicand (that's the expression inside the square root) is x-8, and you cannot have that be negative.

Math people write  'non-negative' as ">= 0",

So here you write:  

x - 8 >= 0
x >= 8

That's your domain.

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