Value Excluded from the DomainDate: 5/23/96 at 21:36:35 From: Anonymous Subject: Algebra II f(x)=3x cubed + x squared - 2x over 9x squared -4 I have to find the value that is excluded from the domain. I don't even know where to start. Date: 5/24/96 at 11:17:29 From: Doctor Ethan Subject: Re: Algebra II Hey Judy, To represent cubed and squared I will use ^ : x cubed is x^3 and x squared is x^2 So your problem is 3x^3 + x^2 - 2x f(x) = ------------------ 9x^2 - 4 Let's see what values of x will give us problems. With things like this there are usually only two things that can go wrong: f(x) can be imaginary (if you don't know what that means, ignore it), and f(x) can be undefined. Problem one happens when we have the square root of a negative number. Problem 2 happens when we have a fraction with zero in the denominator. Since we have no square roots in this problem let's look for problem 2. Are there any values of x that will make the denominator 0? In other words, we need to solve this equation: 9x^2 - 4 = 0 That is, 9x^2 = 4 or x^2 = 4/9 so x = + or - 2/3 So those are the points that cannot be in the domain. Good luck. -Doctor Ethan, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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