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Mathematics 15 Online
OpenStudy (anonymous):

Don't know how to do this help for medal

Mehek (mehek14):

question

OpenStudy (anonymous):

Which value of x is NOT in the domain of the function f(x)=\(23)/(11 x-24)? x=____

jimthompson5910 (jim_thompson5910):

You cannot divide by zero. So if the denominator 11x-24 were equal to zero, then what must the value of x be?

OpenStudy (anonymous):

so 0 is the value of x not in the domain?

jimthompson5910 (jim_thompson5910):

try plugging x = 0 into f(x). Do you run into a division by zero error?

OpenStudy (anonymous):

no

jimthompson5910 (jim_thompson5910):

so x = 0 is a perfectly valid input

jimthompson5910 (jim_thompson5910):

x = 0 is part of the domain

jimthompson5910 (jim_thompson5910):

you need to solve 11x-24 = 0 for x to get the value of x that makes the denominator zero

OpenStudy (anonymous):

24/11

OpenStudy (anonymous):

@jim_thompson5910

jimthompson5910 (jim_thompson5910):

correct, x = 24/11 is the value that when you plug it into 11x - 24, it turns into 0 causing the division by zero error

jimthompson5910 (jim_thompson5910):

to avoid division by zero errors, we kick out any values of x that cause the division by zero errors. So that's why x = 24/11 is not in the domain

OpenStudy (anonymous):

Find the domain of f(x) = sqrt(4 x -5)

OpenStudy (anonymous):

is it 5?

jimthompson5910 (jim_thompson5910):

now you need to make sure that the radicand is never negative

jimthompson5910 (jim_thompson5910):

so force it to be either 0 or positive \[\Large 4x - 5 \ge 0\] solve for x

OpenStudy (anonymous):

x=5/4??

OpenStudy (anonymous):

how do you write it in interval notation?

jimthompson5910 (jim_thompson5910):

it's actually \[\Large x \ge \frac{5}{4}\] when you solve for x

OpenStudy (anonymous):

and how would that be written in interval notion?

jimthompson5910 (jim_thompson5910):

go ahead and write out what you think it looks like and I'll help you from there (if you need any). I want to see how much you know about interval notation.

OpenStudy (anonymous):

(0,5/4)

jimthompson5910 (jim_thompson5910):

the left most edge of the interval \(\Large x \ge \frac{5}{4}\) is 5/4, agreed?

OpenStudy (anonymous):

I don't get it

jimthompson5910 (jim_thompson5910):

\[\Large x \ge \frac{5}{4}\] describes all the numbers that are greater than or equal to 5/4

jimthompson5910 (jim_thompson5910):

the smallest that x can be is 5/4. It cannot get any smaller. So the left edge is 5/4 x can get as large as it wants, so the right edge is infinity

jimthompson5910 (jim_thompson5910):

\[\Large x \ge \frac{5}{4}\] written in interval notation is \[\Large \left[\frac{5}{4},\infty)\right.\]

jimthompson5910 (jim_thompson5910):

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