Questions on Algebra: Functions, Domain, NOT graphing answered by real tutors!

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Question 151704: I need the domain of the following problem: g(x)=5x/x^2+25
Please. College Algebra. If I can figure out the meaning of domain and see it being worked in a problem, I should be able to work it.
: I need the domain of the following problem: g(x)=5x/x^2+25
Please. College Algebra. If I can figure out the meaning of domain and see it being worked in a problem, I should be able to work it.

Answer by jim_thompson5910(9166) About Me  (Show Source):
You can put this solution on YOUR website!
f(x)=(5x)/(x^2+25) Start with the given function


x^2+25=0 Set the denominator equal to zero. Remember, dividing by 0 is undefined. So if we find values of x that make the denominator zero, then we must exclude them from the domain.


x^2=-25 Subtract 25 from both sides.


x=sqrt(-25) Take the square root of both sides.


x=sqrt(-1)*sqrt(25) Factor sqrt(-25) into sqrt(-1)*sqrt(25)


x=i*sqrt(25) Replace sqrt(-1) with "i"


x=5*i or x=-5i Take the square root of 25 to get 5 or -5


Since the values x=5*i or x=-5i make the denominator zero, this means that there are no real x values that make the denominator zero (since 5i and -5i are both complex).


So you can plug in any real number for x and you'll get a result for f(x).



If that doesn't make any sense to you, then try to think of it like this:

x^2 is always positive. So there are no real values that make x^2=-25 true. That's why the domain includes all real numbers.



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Answer:

So the domain of the function in set-builder notation is:





In plain English, this reads: x is the set of all real numbers (In other words, x can be any number)


Also, in interval notation, the domain is: