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

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Question 165631: Can someone please explain to me how to do this problem?
Find the domain of the rational expression.
f(x)=3x+1
_____
x-5
Thanks
: Can someone please explain to me how to do this problem?
Find the domain of the rational expression.
f(x)=3x+1
_____
x-5
Thanks

Answer by jim_thompson5910(9869) About Me  (Show Source):
You can put this solution on YOUR website!

f(x)=(3x+1)/(x-5) Start with the given function


x-5=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=0+5Add 5 to both sides


x=5 Combine like terms on the right side





Since x=5 makes the denominator equal to zero, this means we must exclude x=5 from our domain

So our domain is:

which in plain English reads: x is the set of all real numbers except x CANNOT equal 5

So our domain looks like this in interval notation


note: remember, the parenthesis excludes 5 from the domain

If we wanted to graph the domain on a number line, we would get:

drawing(500,50,-10,10,-10,10,<BR>
number_line( 500, -5, 15),<BR>
blue(arrow(0.2,-7,10,-7)),<BR>
blue(arrow(0.2,-6.5,10,-6.5)),<BR>
blue(arrow(0.2,-6,10,-6)),<BR>
blue(arrow(0.2,-5.5,10,-5.5)),<BR>
blue(arrow(0.2,-5,10,-5)),<BR>
blue(arrow(-0.2,-7,-10,-7)),<BR>
blue(arrow(-0.2,-6.5,-10,-6.5)),<BR>
blue(arrow(-0.2,-6,-10,-6)),<BR>
blue(arrow(-0.2,-5.5,-10,-5.5)),<BR>
blue(arrow(-0.2,-5,-10,-5)),
<BR>

circle(0,-5.8,0.35),<BR>
circle(0,-5.8,0.4),<BR>
circle(0,-5.8,0.45),<BR>
circle(0,-5.8,0.4),<BR>
circle(0,-5.8,0.45)<BR>
) Graph of the domain in blue and the excluded value represented by open circle

Notice we have a continuous line until we get to the hole at x=5 (which is represented by the open circle).
This graphically represents our domain in which x can be any number except x cannot equal 5