Thanks Nelson, yes it is -3 for question 2; I did it again earlier today. As for the plague of the first question, I get stuck when I get derivative of sqrt(x), which is 1/2x^-1/2, read as: one half x to the power of negative one half power. Also, the derivatives of sqrt(x) and sqrt(x)-1 are the same. Right? What do I get after multiplying: sqrt(x) * 1/2x^-1/2 Back to question 3, the derivative of: -3/(x^2-2x+1) I get is: (-2(x+1))/3. Correcto? Cheers! Ned ----- Original Message ----- From: Nelson Blachman To: maths@xxxxxxxxxxxxx Sent: Tuesday, November 07, 2006 4:12 PM Subject: [maths] Re: calculus; more derivatives Ned, The answer to your first question is: No. Please show your work to indicate how you've misused the hints I gave you. The answer you give for the second question llooks almost right; I get -3 where you got 3. The answer to your 3rd question is that the derivative with respect to x of 3/z is -3(dz/dx)/z^2. HTH Nelson ----- Original Message ----- From: Ned Granic To: maths@xxxxxxxxxxxxx Sent: Tuesday, November 07, 2006 12:17 PM Subject: [maths] calculus; more derivatives SO, here I go again: Is 2/x the derivative of [(sqrt(x)-1)/sqrt(x)]+1? And: Is 3/((x-1)^2) the derivative of: (2x+1)/(x-1)? And: How to find the derivative of: 3/(x^2 - 2x + 1)? Many thanks in advance! Ned