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Mathematics 20 Online
OpenStudy (katherinesmith):

What is the approximate value of the function at x = 1? graph inside --->

OpenStudy (katherinesmith):

OpenStudy (katherinesmith):

@jim_thompson5910

jimthompson5910 (jim_thompson5910):

look at the graph locate x = 1 on the x axis and see where it lands on the curve

jimthompson5910 (jim_thompson5910):

the value of the function is equal to the y coordinate of the point at x = 1

OpenStudy (katherinesmith):

that sentence just killed my brain cells

jimthompson5910 (jim_thompson5910):

what's not making sense?

OpenStudy (katherinesmith):

wait wait wait. so the curve lands on -0.75 correct? because once it touches that box that's where its closest to

jimthompson5910 (jim_thompson5910):

yeah roughly, you are correct

jimthompson5910 (jim_thompson5910):

when x = 1, y is y = -0.75 roughly

OpenStudy (katherinesmith):

do you know how to find the range and domain of functions

jimthompson5910 (jim_thompson5910):

yes I do

OpenStudy (katherinesmith):

find the range of \[f (x) = \frac{ 2 }{ x - 3 } - 5\]

jimthompson5910 (jim_thompson5910):

how would you find the horizontal asymptote of that

OpenStudy (katherinesmith):

i have no idea... don't think i've learned that

jimthompson5910 (jim_thompson5910):

oh wait, I didn't simplify first, hold on

jimthompson5910 (jim_thompson5910):

\[f (x) = \frac{ 2 }{ x - 3 } - 5\] \[f (x) = \frac{ 2 }{ x - 3 } - 5\frac{x-3}{x-3}\] \[f (x) = \frac{ 2 }{ x - 3 } - \frac{5(x-3)}{x-3}\] \[f (x) = \frac{ 2 }{ x - 3 } - \frac{5x-15}{x-3}\] \[f (x) = \frac{ 2 - (5x-15) }{ x - 3 }\] \[f (x) = \frac{ 2 - 5x+15 }{ x - 3 }\] \[f (x) = \frac{ -5x + 17 }{ x - 3 }\] Since the degree of the numerator equals the degree of the denominator (they are both equal to 1), this means that the horizontal asymptote is y = -5/1 = -5

jimthompson5910 (jim_thompson5910):

the range in interval notation is (-infinity, -5) U (-5, infinity)

OpenStudy (katherinesmith):

i think i understand. now what about the domain of a different problem

OpenStudy (katherinesmith):

\[f (x) = \frac{ 1 }{ x + 1 } - 4\]

jimthompson5910 (jim_thompson5910):

hint: you cannot divide by zero

OpenStudy (katherinesmith):

now that i know how to find the range i need to know how to find the domain.

jimthompson5910 (jim_thompson5910):

if you cannot divide by zero, what does that mean for the domain?

OpenStudy (katherinesmith):

no solution?

jimthompson5910 (jim_thompson5910):

let's say the denominator was zero, so that would mean that x+1 = 0 what is x?

OpenStudy (katherinesmith):

-1

jimthompson5910 (jim_thompson5910):

therefore, if x = -1, then x+1 is zero

jimthompson5910 (jim_thompson5910):

which means that you can plug in any value you want for x...BUT...x cannot be -1

jimthompson5910 (jim_thompson5910):

x cannot be -1 to avoid division by zero everything else is just fine

OpenStudy (katherinesmith):

so the domain is all real numbers except -1

jimthompson5910 (jim_thompson5910):

exactly

OpenStudy (katherinesmith):

thank you! alright next question,

OpenStudy (katherinesmith):

\[\frac{ 2x - 5 }{ x - 2 } - 2 = \frac{ 3 }{ x + 2 }\]

jimthompson5910 (jim_thompson5910):

\[\frac{ 2x - 5 }{ x - 2 } - 2 = \frac{ 3 }{ x + 2 }\] \[\frac{ 2x - 5 }{ x - 2 } - 2\frac{x-2}{x-2} = \frac{ 3 }{ x + 2 }\] \[\frac{ 2x - 5 }{ x - 2 } - \frac{2(x-2)}{x-2} = \frac{ 3 }{ x + 2 }\] \[\frac{ 2x - 5 }{ x - 2 } - \frac{2x-4}{x-2} = \frac{ 3 }{ x + 2 }\] \[\frac{ 2x - 5-(2x-4)}{x-2} = \frac{ 3 }{ x + 2 }\] \[\frac{ 2x - 5-2x+4}{x-2} = \frac{ 3 }{ x + 2 }\] I'll let you finish

OpenStudy (katherinesmith):

@jim_thompson5910 i got x = 1

jimthompson5910 (jim_thompson5910):

you are correct

OpenStudy (katherinesmith):

thank god you literally saved my life

jimthompson5910 (jim_thompson5910):

not really lol, but I'm glad to be of help

OpenStudy (katherinesmith):

i do have another if you wanna stick around \[\frac{ x - 4 }{ 4 } + \frac{ x }{ 3 } = 6\]

OpenStudy (katherinesmith):

@jim_thompson5910

jimthompson5910 (jim_thompson5910):

I'll start you off \[\frac{ x - 4 }{ 4 } + \frac{ x }{ 3 } = 6\] \[\frac{ 3*(x - 4) }{ 3*4 } + \frac{ 4x }{ 4*3 } = 6\] \[\frac{ 3x - 12 }{ 12 } + \frac{ 4x }{ 12 } = 6\] \[\frac{ 3x - 12 + 4x }{ 12 } = 6\]

OpenStudy (katherinesmith):

can you cancel -12 and 12 to get rid of your denominator?

jimthompson5910 (jim_thompson5910):

no

jimthompson5910 (jim_thompson5910):

that is not a valid algebraic move

OpenStudy (katherinesmith):

x = 12

jimthompson5910 (jim_thompson5910):

good

OpenStudy (katherinesmith):

now i have another domain question

OpenStudy (katherinesmith):

\[f(x) = \frac{ 2 }{ x + 1 } - 3\]

jimthompson5910 (jim_thompson5910):

tell me what you get

OpenStudy (katherinesmith):

all real numbers except -1

jimthompson5910 (jim_thompson5910):

you are correct

OpenStudy (katherinesmith):

then what is the domain of \[f (x) = - \frac{ 3 }{ x - 4 } + 2\]

OpenStudy (katherinesmith):

would it be all real numbers except 4?

jimthompson5910 (jim_thompson5910):

very good

jimthompson5910 (jim_thompson5910):

you got the hang of this domain stuff

OpenStudy (katherinesmith):

yessss okay next one

OpenStudy (katherinesmith):

\[\frac{ 3 }{ n - 1 } + \frac{ 2 }{ 3 } = \frac{ 5 }{ 3 }\]

jimthompson5910 (jim_thompson5910):

\[\large \frac{ 3 }{ n - 1 } + \frac{ 2 }{ 3 } = \frac{ 5 }{ 3 }\] \[\large \frac{ 3*3 }{ 3(n - 1) } + \frac{ 2(n-1) }{ 3(n-1) } = \frac{ 5 }{ 3 }\] \[\large \frac{ 9 }{ 3(n - 1) } + \frac{ 2n-2 }{ 3(n-1) } = \frac{ 5 }{ 3 }\] \[\large \frac{ 9 + 2n-2 }{ 3(n-1) } = \frac{ 5 }{ 3 }\]

OpenStudy (katherinesmith):

n = 4

jimthompson5910 (jim_thompson5910):

correct

OpenStudy (katherinesmith):

you are the bomb

OpenStudy (katherinesmith):

i have 3 questions left

OpenStudy (katherinesmith):

\[\frac{ 4 }{ n } - \frac{ 1 }{ 2 } = -\frac{ 6 }{ 3n }\]

jimthompson5910 (jim_thompson5910):

\[\large \frac{ 4 }{ n } - \frac{ 1 }{ 2 } = -\frac{ 6 }{ 3n }\] \[\large \frac{ 2*4 }{ 2*n } - \frac{ n*1 }{ n*2 } = -\frac{ 6 }{ 3n }\] \[\large \frac{ 8 }{ 2n } - \frac{ n }{ 2n } = -\frac{ 6 }{ 3n }\] \[\large \frac{ 8 - n }{ 2n } = -\frac{ 6 }{ 3n }\]

OpenStudy (katherinesmith):

i got 12n = 24n - 3n..... they all have n's

jimthompson5910 (jim_thompson5910):

\[\large \frac{ 4 }{ n } - \frac{ 1 }{ 2 } = -\frac{ 6 }{ 3n }\] \[\large \frac{ 2*4 }{ 2*n } - \frac{ n*1 }{ n*2 } = -\frac{ 6 }{ 3n }\] \[\large \frac{ 8 }{ 2n } - \frac{ n }{ 2n } = -\frac{ 6 }{ 3n }\] \[\large \frac{ 8 - n }{ 2n } = -\frac{ 6 }{ 3n }\] \[\large 3n(8 - n) = -6*2n\] \[\large 24n - 3n^2 = -12n\] does that help?

OpenStudy (katherinesmith):

now what the heck am i supposed to do

jimthompson5910 (jim_thompson5910):

\[\large 24n - 3n^2 = -12n\] \[\large 24n - 3n^2 + 12n = 0\] \[\large -3n^2 + 36n = 0\] \[\large -3n(n - 12) = 0\] how about now?

jimthompson5910 (jim_thompson5910):

don't forget about checking your answers and keep the domain in mind

OpenStudy (katherinesmith):

n = 0 and n = 12?

jimthompson5910 (jim_thompson5910):

check both of those only one is the true answer

OpenStudy (katherinesmith):

12

jimthompson5910 (jim_thompson5910):

good

OpenStudy (katherinesmith):

i have 2 left and they're super quick graph ones

OpenStudy (katherinesmith):

What is the approximate value of the function at x = 0?

jimthompson5910 (jim_thompson5910):

you tell me

OpenStudy (katherinesmith):

i don't know...4?

jimthompson5910 (jim_thompson5910):

you're looking at the point when y = 0

jimthompson5910 (jim_thompson5910):

how about x = 0

OpenStudy (katherinesmith):

1.3 ?

jimthompson5910 (jim_thompson5910):

close enough

OpenStudy (katherinesmith):

last one! What is the approximate value of the function at x =5

jimthompson5910 (jim_thompson5910):

again tell me what you got

OpenStudy (katherinesmith):

this one i really don't know.

jimthompson5910 (jim_thompson5910):

find x = 5 on the x axis

jimthompson5910 (jim_thompson5910):

draw a vertical line through x = 5 find where that vertical line crosses the red curve

OpenStudy (katherinesmith):

-0.75?

jimthompson5910 (jim_thompson5910):

then report the y coordinate

jimthompson5910 (jim_thompson5910):

yes approximately

OpenStudy (katherinesmith):

i got every single one right... i actually wanna cry. thank you beyond words. @jim_thompson5910

jimthompson5910 (jim_thompson5910):

you're welcome

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