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OpenStudy (mathmusician):

Question about the fundamental theorems of calculus

OpenStudy (mathmusician):

\[d/dx \int\limits_{-3}^{1}\]

OpenStudy (mathmusician):

2t^3+3dt

OpenStudy (freckles):

your question doesn't seem right and if it is you are taking derivative of a constant...

OpenStudy (mathmusician):

there are options

OpenStudy (freckles):

and derivative of a constant is...

OpenStudy (mathmusician):

0

OpenStudy (mathmusician):

the second equation i wrote is part of the first one

OpenStudy (freckles):

I don't see an equation I see an expression

OpenStudy (freckles):

\[\int\limits_{-3}^{1} f(t) dt=\text{ some constant number } \\ \frac{d}{dx} \int\limits_{-3}^{1} f(t) dt=\frac{d}{dx}(\text{ some constant number} )=0\]

OpenStudy (mathmusician):

\[d/dx \int\limits_{-3}^{1} (2t ^{3}+3) dt\]

OpenStudy (mathmusician):

the choices are a. 2t^3 + 3 b. 56.0 c. 5 d. -28.0 e. none of these

OpenStudy (freckles):

do you have anymore questions on this one?

OpenStudy (freckles):

do you understand that the definite integral is going to be a constant ?

OpenStudy (freckles):

by d/dx next to that means we have to differentiate that result

OpenStudy (mathmusician):

yes

OpenStudy (mathmusician):

the derivative of any constant is 0

OpenStudy (freckles):

yep

OpenStudy (mathmusician):

but that isnt one of the choices unless there are more steps

OpenStudy (freckles):

i thought you listed none of these

OpenStudy (freckles):

none of these means none of the above

OpenStudy (freckles):

and 0 wasn't listed above so it has to be none of these

OpenStudy (mathmusician):

I know that F'(x) = f(x) right?

OpenStudy (freckles):

yes assuming F is some antiderivative of f

OpenStudy (mathmusician):

yah

OpenStudy (mathmusician):

so would that make it option a?

OpenStudy (freckles):

no derivaitve of a constant is not 2t^3+3

OpenStudy (mathmusician):

or is that different because it is f(t) instead of f(x)

OpenStudy (freckles):

\[\int\limits_a^b f(t) dt \text{ if this exists } \\ \text{ will be a constant if the upper\lower limit is not a variable }\]

OpenStudy (mathmusician):

\[F'(x) = d/dx (\int\limits_{a}^{x} f(x) dt) = f(x)\]

OpenStudy (mathmusician):

that is one of the fundamental theorems that i think im supposed to use

OpenStudy (freckles):

do you understand both of your limits are constants? not one of them is a variable

OpenStudy (mathmusician):

okay so none of these

OpenStudy (mathmusician):

i would only use that if one was a variable?

OpenStudy (freckles):

but fine if you want to use \[\frac{d}{dx} \int\limits_a^{x} f(t) dt=f(x) \\ \text{ then rewrite } \int\limits_{-3}^{1} f(t) dt \text{ as } \int\limits_{-3}^{x} f(t)+\int\limits_x^{1} f(t) dt =\int\limits_{-3}^{x}f(t) dt-\int\limits_{1}^{x} f(t) dt \\ \text{ so } \frac{d}{dx}(\int\limits_{-3}^{1} f(t) dt)=\frac{d}{dx}(\int\limits_{-3}^{x} f(t) dt-\int\limits_1^x f(t) dt) \\ \frac{d}{dx} \int\limits_{-3}^{1} f(t) dt=\frac{d}{dx} \int\limits_{-3}^{x } f(t) dt - \frac{d}{dx } \int\limits_1^{x} f(t) dt \\ \frac{d}{dx} \int\limits_{-3}^1 f(t) dt=f(x)-f(x) \\ \frac{d}{dx} \int\limits_{-3}^{1} f(t) dt=0\] but all of this work is totally unnecessary given we should know that the definite integral we are differentiating is a constant

OpenStudy (mathmusician):

yah you are right thankyou

OpenStudy (freckles):

you could use the fundamental theorem if one or more is a variable however if both are constant you could shove a variable in between those constants and do fundamental theorem of calculus but it is totally totally unnecessary

OpenStudy (mathmusician):

if you feel like it could you help me with one more

OpenStudy (freckles):

sure

OpenStudy (mathmusician):

OpenStudy (freckles):

first what is h'(x)?

OpenStudy (freckles):

use that fundamental theorem of calculus you were trying to mention before

OpenStudy (mathmusician):

okay one sec

OpenStudy (mathmusician):

f(t)?

OpenStudy (freckles):

well f(x)

OpenStudy (freckles):

h'(x)=f(x)

OpenStudy (freckles):

so we are looking at a graph of h'(x)

OpenStudy (mathmusician):

what is f(x) though?

OpenStudy (freckles):

f(x) is the graph which is also h'(x)

OpenStudy (mathmusician):

f(t) is the actual function so is f(x) some other function or the curve?

OpenStudy (freckles):

looking at the graph where is h'(3) aka f(3)

OpenStudy (mathmusician):

okay

OpenStudy (mathmusician):

-5

OpenStudy (freckles):

h'(3)=f(3)=-5 but choice a says h'(3)>0

OpenStudy (freckles):

but -5>0 is not true

OpenStudy (mathmusician):

not true okay what about the other 2?

OpenStudy (freckles):

one at a time

OpenStudy (freckles):

okay to find the critical number of h' we must look at h'' and find when h''=0 to find the critical numbers of h we must look at h' and find when h'=0 let's do the latter first because it is much easier

OpenStudy (freckles):

so we are actually looking at choice 3 right now

OpenStudy (freckles):

h(x) has a relative maximum at x=5? trying to see if this is true or false... so we need to find the critical numbers of h we start by finding h' (we done this; it is f which is the graph given) we look to see where h'=0

OpenStudy (freckles):

what x values do you have h' is 0?

OpenStudy (freckles):

this means at what x values does h' aka f cross the x-axis

OpenStudy (mathmusician):

2,4, and 6

OpenStudy (freckles):

right so x=5 isn't even a contender to be a max or min since it wasn't even a critical number of h

OpenStudy (mathmusician):

wait but it is the highest point within that area so woldnt that make it a relative max? and the global max would be at 1

OpenStudy (freckles):

you are looking at the graph of h' not the graph of h

OpenStudy (mathmusician):

oh okay

OpenStudy (freckles):

for part 2 you actually don't need to find the second derivative like I mentioned since the graph of h' is given the only problem is x=2 is also not a relative max of h' h' has a global max/relative max occurring at x=1 h' has a global min/relative min occurring at x=3 h' has a relative max occurring at x=5 And there looks like h' has a relative min occurring at x=6.6 approximately

OpenStudy (freckles):

That first line does say the function f(t) is graphed below right? like there isn't like a prime symbol I'm missing there right?

OpenStudy (mathmusician):

that is what it says

OpenStudy (mathmusician):

so it seems like the only one that is true is III

OpenStudy (freckles):

I'm pretty sure none of them are true The critical numbers of h is when h'=0 which is when x=2,4,6 x=5 wasn't included in those numbers

OpenStudy (freckles):

these all seem false to me

OpenStudy (freckles):

oops x=0,2,4,6,8 if you want to include the endpoints

OpenStudy (mathmusician):

so none of them are true?

OpenStudy (freckles):

nope

OpenStudy (mathmusician):

okay well thank you for your help!!

OpenStudy (freckles):

weird both questions you asked are none of these

OpenStudy (mathmusician):

yah that is why i was trying to make sure that you were right because i never really get those kind of answers

OpenStudy (freckles):

all of these would have been right: h'(3)<0 h'(x) has a relative maximum at x=5. h(x) has a relative maximum at x=2.

OpenStudy (mathmusician):

wait they are all RIGHT?

OpenStudy (freckles):

like if the sign in the first one has been switched or if the x=2 and x=5 has been switched in the last two options

OpenStudy (freckles):

no you aren't reading what I wrote if you think that :p

OpenStudy (freckles):

your choices were h'(3)>0 h'(x) has a relative maximum at x=2 h(x) has a relative maximum at x=5 which are all incorrect

OpenStudy (mathmusician):

oh nevermind

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