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Mathematics 14 Online
OpenStudy (babynini):

Differentiate with e

OpenStudy (babynini):

\[y=\frac{ ae^x+b }{ ce^x+d }\]y'=?

OpenStudy (tkhunny):

Have we attempted the Quotient Rule? What has "e" to do with it?

OpenStudy (babynini):

\[\frac{ (ce^x+d)(ae^x+b)'-(ae^x+b)(ce^x+d)' }{ (ce^x+d)^2 }\]erm yeah, I did this. But i'm not sure how to differentiate with those a's and b's and e's. E becaue of the e^x's in there.

OpenStudy (babynini):

I mean, are c,d,b, a all constants? do they become 1?

OpenStudy (tkhunny):

That';s good. \((ae^{x}+b)' = ae^{x}\) a, b, c, d, and e are just constants. e is a specific constant. The others are arbitrary.

OpenStudy (tkhunny):

\(\dfrac{d}{dx}a = 0\) \(\dfrac{d}{dx}e = 0\) \(\dfrac{d}{dx}a^{x} = a^{x}\ln(a)\) \(\dfrac{d}{dx}e^{x} = e^{x}\ln(e) = e^{x}\)

OpenStudy (babynini):

hmm ok. so in ae^x the a stays there because it is.."attached" to e?

OpenStudy (tkhunny):

It's just a constant and comes along for the ride.

OpenStudy (tkhunny):

\(\dfrac{d}{dx}ae^{x} = a\dfrac{d}{dx}e^{x} = ae^{x}\)

OpenStudy (tkhunny):

\(\dfrac{d}{dx}(ae)^{x} = (ae)^{x}\ln(ae) = (ae)^{x}(\ln(a)+1)\)

OpenStudy (tkhunny):

Try a few examples and get used to what is a constant and what isn't.

OpenStudy (babynini):

Ohh I see! That makes more sense written that way with the a before the d/dx

OpenStudy (babynini):

\[\frac{ e^x(ad-bc) }{ (c^ex+d)^2}\]=y'

OpenStudy (babynini):

oops that botton was meant to be ce^x

OpenStudy (tkhunny):

I think you have it! Good work. Very often, there will be some odd simplification with the denominator. I don't see any, this time. Keep your eyes out for it.

OpenStudy (babynini):

Thanks so much! :)

OpenStudy (babynini):

ah ok. In this one there was just a lot of multiplying in and then taking back out again xD

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