sysD Posted January 19, 2012 Share Posted January 19, 2012 (edited) Hi, [math]3x/(x^2+4)[/math] I want to find the derivative of this but I can't use the quotient rule. So I figure I'll use the chain/product rule. I'm new to calc though. Do I use both? Or just one? [math]= 3x(x^2 +4)^-1[/math] [math]=-3x(2x(x^2+4)^-2[/math] That's the chain rule I think. Do I go on to use the product rule? Edited January 19, 2012 by sysD Link to comment Share on other sites More sharing options...

mathematic Posted January 19, 2012 Share Posted January 19, 2012 You need to use both (you used the chain rule properly to get one term) - add in the term containing the derivative of 3x. Link to comment Share on other sites More sharing options...

Bignose Posted January 20, 2012 Share Posted January 20, 2012 I want to find the derivative of this but I can't use the quotient rule. So I figure I'll use the chain/product rule. The quotient rule is just a special case. And, exactly why can't you use it? Link to comment Share on other sites More sharing options...

DrRocket Posted January 21, 2012 Share Posted January 21, 2012 The quotient rule is just a special case. And, exactly why can't you use it? His ruler is broken ? 1 Link to comment Share on other sites More sharing options...

shah_nosrat Posted March 4, 2012 Share Posted March 4, 2012 Hi, [math]3x/(x^2+4)[/math] [math]= 3x(x^2 +4)^-1[/math] [math]=-3x(2x(x^2+4)^-2[/math] That's the chain rule I think. Do I go on to use the product rule? Hi, You can use the product and chain rule together. Remember the product rule says to differentiate [math]3x[/math] and keep [math](x^2 + 4)^-1[/math] and continue the procedure (which can be found in any Calculus Textbook) and also remembering the chain rule when differentiating [math](x^2 + 4)^-1[/math] Now, [math]=-3x(2x(x^2+4)^-2[/math] this is one of the terms but you're missing one more term to get the answer NB: Using the quotient rule is more direct! Hope this helps! Link to comment Share on other sites More sharing options...

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