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OpenStudy (anonymous):
jimthompson5910 (jim_thompson5910):
Average rate of change on the interval [a,b] for f(x)
\[\Large m = \frac{f(b)-f(a)}{b-a}\]
m is the average rate of change
OpenStudy (anonymous):
the part where it says solve on this interval confuses me, i don't know how to get that
OpenStudy (anonymous):
thank your for taking the time to help me, greatly appreciate it
jimthompson5910 (jim_thompson5910):
we have
f(t) = 4t^2 - 1
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jimthompson5910 (jim_thompson5910):
what is f(5) ?
OpenStudy (anonymous):
the domain?
jimthompson5910 (jim_thompson5910):
no what happens when you plug t = 5 into f(t) = 4t^2 - 1
jimthompson5910 (jim_thompson5910):
f(t) = 4t^2 - 1
f(5) = 4(5)^2 - 1 ... replace every 't' with 5
f(5) = ???
OpenStudy (anonymous):
oh 99!!!!
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jimthompson5910 (jim_thompson5910):
what is f(5.1) equal to
OpenStudy (anonymous):
5.1 or 5? dont i plug in 5
jimthompson5910 (jim_thompson5910):
when we say f(5.1) and when f(t) = 4t^2 - 1, we are replacing every t with 5.1
jimthompson5910 (jim_thompson5910):
f(3) means replace every t with 3
etc etc
OpenStudy (anonymous):
4(5.1)^2-1=103.04
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jimthompson5910 (jim_thompson5910):
so we know this
f(5) = 99
f(5.1) = 103.04
jimthompson5910 (jim_thompson5910):
we now plug that into the formula
\[\Large m = \frac{f(b)-f(a)}{b-a}\]
in this case
a = 5
b = 5.1
jimthompson5910 (jim_thompson5910):
so...
\[\Large m = \frac{f(b)-f(a)}{b-a}\]
\[\Large m = \frac{f(5)-f(5.1)}{5-5.1}\]
\[\Large m = \frac{99-103.04}{5-5.1}\]
\[\Large m = \frac{-4.04}{-0.1}\]
\[\Large m = 40.4\]
OpenStudy (anonymous):
perfect!!! thank you!!!!!
jimthompson5910 (jim_thompson5910):
oh sry I have a = 5.1 and b = 5 but it really doesn't matter (since you can swap a and b easily)
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jimthompson5910 (jim_thompson5910):
anyways, the average rate of change is 40.4
this represents the slope of the line through (5, 99) and (5.1, 103.04)
OpenStudy (anonymous):
so my final 3 answers? i don't get how the web assign system wants it
jimthompson5910 (jim_thompson5910):
so that's why it looks very similar to the slope formula (because in a way, it is the slope formula)
jimthompson5910 (jim_thompson5910):
do you know how to find the derivative?
OpenStudy (anonymous):
oh genius!
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OpenStudy (anonymous):
no! i was having a lot of trouble yesterday with that
jimthompson5910 (jim_thompson5910):
have you learned about calculus topics yet? like limits and derivatives
OpenStudy (anonymous):
i am taking this class online and I've tried, but its harder online
OpenStudy (anonymous):
technically according to my homework i should know them already...
jimthompson5910 (jim_thompson5910):
so the lesson plan isn't that nailed down
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OpenStudy (anonymous):
not at all!!
jimthompson5910 (jim_thompson5910):
ok well when you get free time, I recommend you read over these notes
http://tutorial.math.lamar.edu/Classes/CalcI/CalcI.aspx
go through it and see what makes sense and what doesn't. Then you can come back here and ask questions on stuff you don't get
jimthompson5910 (jim_thompson5910):
anyways, you'll use derivatives to derive f(t) to get f ' (t)
this will give you a function that allows you to find the instantaneous rate of change at any point
OpenStudy (anonymous):
thank you, the link has been saved, and will look at it after i finish these problems!
OpenStudy (anonymous):
okay
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so
f(t) = 4t^2 - 1
d/dt [f(t]) = d/dt[4t^2 - 1]
f ' (t) = 2*4t^(2-1)
f ' (t) = 8t
OpenStudy (anonymous):
im familiar with the power rule, i just always apply it at worng times!
OpenStudy (anonymous):
okay.
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jimthompson5910 (jim_thompson5910):
what is f ' (5) equal to?
OpenStudy (anonymous):
thank you for all the links!
OpenStudy (anonymous):
99?
jimthompson5910 (jim_thompson5910):
f ' (t) = 8t
f ' (5) = 8*5
f ' (5) = 40
jimthompson5910 (jim_thompson5910):
so the instantaneous rate of change at t = 5 is 40
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jimthompson5910 (jim_thompson5910):
notice how it's pretty close to that average rate of change we got before, which was 40.4
OpenStudy (anonymous):
yes!!!!! i see it clearly, but without help i won't figure it out
jimthompson5910 (jim_thompson5910):
you will once you practice more and read over notes like what I posted
OpenStudy (anonymous):
thank you! i will!
jimthompson5910 (jim_thompson5910):
you're welcome
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OpenStudy (anonymous):
so then my answers are 40 at t5 and 40.1 at t5.1
jimthompson5910 (jim_thompson5910):
not 40.1
OpenStudy (anonymous):
40.1 goes on the top
jimthompson5910 (jim_thompson5910):
f ' (t) = 8t
f ' (5.1) = 8*5.1
f ' (5.1) = 40.8
jimthompson5910 (jim_thompson5910):
the instantaneous rate of change at t = 5.1 is 40.8
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OpenStudy (anonymous):
and the top answer? the first empty box?
jimthompson5910 (jim_thompson5910):
that was the avg rate of change, aka the slope of the line through (5, 99) and (5.1, 103.04)
jimthompson5910 (jim_thompson5910):
this is what I get
OpenStudy (anonymous):
i thought that one is 40.4?
jimthompson5910 (jim_thompson5910):
the last one, you'll do
V(s) = s^3
V ' (s) = 3s^2
V ' (19) = 3*19^2
V ' (19) = 1083
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OpenStudy (anonymous):
this is what i have
jimthompson5910 (jim_thompson5910):
correct so far
OpenStudy (anonymous):
of course because you gave them to me! lol
OpenStudy (anonymous):
thank you for the second question:)
jimthompson5910 (jim_thompson5910):
lol well hopefully it's clicking that you could find similar problems in the future
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jimthompson5910 (jim_thompson5910):
np
OpenStudy (anonymous):
I'm going to practice different versions after i get this one correctly
jimthompson5910 (jim_thompson5910):
good idea
OpenStudy (anonymous):
OpenStudy (anonymous):
i think I'm done?
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OpenStudy (anonymous):
no its .8?
OpenStudy (anonymous):
the only one left is we just subtract 40.8-40
jimthompson5910 (jim_thompson5910):
see this
jimthompson5910 (jim_thompson5910):
\[\Large m = \frac{f(b)-f(a)}{b-a}\]
\[\Large m = \frac{f(5)-f(5.1)}{5-5.1}\]
\[\Large m = \frac{99-103.04}{5-5.1}\]
\[\Large m = \frac{-4.04}{-0.1}\]
\[\Large m = 40.4\]
OpenStudy (anonymous):
oh gosh i was so wrong!!!
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OpenStudy (anonymous):
thank you it was all right!
OpenStudy (anonymous):
do u want to help me with my last one? I'll really try to do it?
jimthompson5910 (jim_thompson5910):
ok go ahead and post it
OpenStudy (anonymous):
OpenStudy (anonymous):
:) Thank you
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