#Help wihere the random constant come out?

59 messages · Page 1 of 1 (latest)

narrow nova
clear prawnBOT
pine finch
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is this the answer that was presented to you or is part of the development of the answer?

narrow nova
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answer that is presented to me

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they integrated 1/ax+b and got that

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i was wondering where the 1/a lnk came from

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even if it did cancel out

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this is the question

pine finch
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the only thing that i can think of is that they used the literal antiderivative of 1/(ax+b)

narrow nova
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well i mean it could just be 1/(ax+b+c) or something

pine finch
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that is (1/a)(ln(ax+b) +C)

narrow nova
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still how is c = 1/a lnk

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completely random lol

pine finch
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they just set the constant to look like ln(k)

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then distributed the 1/a inside the parentesis

narrow nova
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well its 1/a ln|ax+b| + c

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idk some other people might know

pine finch
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the book author chose to write the constant in a different way

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ln(k) = C

narrow nova
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and what about 1/a?

pine finch
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when you solve for the antiderivative you get a 1/a factor

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so you get (1/a)C = (1/a)ln(k)

narrow nova
pine finch
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not really

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it's actually (1/a)(ln(ax+b) +C)

narrow nova
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well if you differentiate (1/a)ln(ax+b) +C you get 1/ax+b

narrow nova
pine finch
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you set the integral of 1/(ax+b)

narrow nova
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ok

pine finch
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then you multiply by a a/a factor so you get 1/a times integral of a/(ax+b)

narrow nova
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?

pine finch
# narrow nova ?

so you have in the integral argument the derivative of the ln(ax+b)

narrow nova
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thats what the book says

pine finch
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now this is the kind of not skiping any steps way

narrow nova
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ok fine

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i guess my book isnt that rigorous

pine finch
narrow nova
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i mean its the same thing just your way is more rigorous but my way in the textbook is more intuitive?

pine finch
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so in many books or developments they just leav it as C

narrow nova
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ok ok

pine finch
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hope this healped clear the confusion

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bye now

narrow nova
pine finch
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the derivative of ln(ax+b)=a/(ax+b)

narrow nova
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ok

pine finch
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in the ontegral we have just 1/(ax+b)

narrow nova
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ah ok i see

pine finch
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ok now i go

narrow nova
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fair, cya

pine finch
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bye

thick flint
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the example you provided is a definite integral