The Student Room Group

C4 differentiation

Can I use the chain rule to differentiate this function with respect to x?

(xy)1/2
Reply 1
I'd have thought you would use the product rule
(edited 10 years ago)
Reply 2
yup. use also product rule for implicitly differentiating the "xy"
Reply 3
Original post by Hasufel
yup. use also product rule for implicitly differentiating the "xy"


oh okay so because the whole thing is to the power of a half I can use the chain rule? i would have thought you would have to use the product rule throughout?
Reply 4
both.
ddx(xy)1/2=ddx(u)1/2=(12u1/2)dudx\frac{d}{dx} (xy)^{1/2}=\frac{d}{dx}(u)^{1/2}=(\frac{1}{2}u^{-1/2})\frac{du}{dx}

and for du/dx = ddx(xy)\frac{d}{dx}(xy) implicitly
Reply 5
you can split it, (x^(1/2)y^(1/2)) and use the product rule, but there`s too many fractional powers for my liking (personal taste)
Reply 6
but then if that can be done by the chain rule, that would mean you could differentiate xy by the chain rule, but you would need to use the product rule to differentiate xy

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