Posted by **Nicole** on Saturday, March 5, 2011 at 7:23pm.

I have been asked to solve this two different ways. The first way is to use the chain rule and then simplify (which I have already done properly), and the second way is to simplify and then differentiate (not necessarily with the chain rule). I am stuck on how to simplify this question and then how to differentiate it.

Square Root(9x^2) ??

Also I am stuck on how to use the chain rule to differentiate and then simplify this question, as well as the second way where I have to simplify and then differentiate it:

(8x^3)^2/3

I would appreciate if someone would be able to explain these two questions to me, thank you.

- calculus -
**Damon**, Saturday, March 5, 2011 at 7:33pm
y = [ 9 x^2 ] ^.5 ??

let z = 9 x^2 then dz/dx = 18 x

then we have y = z^.5

dy/dz = .5 z^-.5 = .5/3x

but chain rule

dy/dx = dy/dz*dz/dx (.5 /3x)(18 x)

= 9/3 = 3 at last

simplify first

y = (9 x^2)^.5 = 3x

dy/dx = 3 the end

- calculus -
**Damon**, Saturday, March 5, 2011 at 7:37pm
(8x^3)^2/3

I am not going to struggle through that with the chain rule. Go about it the same way as I did upstairs, z = 8 x^3

simplify method:

remember (8x^3)^(1/3) = 2x

(2x)^2 = 4 x^2

y = 4x^2

dy/dx = 8 x the end

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