Posted by bana on August 25, 2002 at 19:15:20:
In Reply to: Re: second derivative posted by Soroban on August 25, 2002 at 02:42:52:
: : how do u find the second derivative of
: : y=5x^2In(x+6)
: Find the first derivative. Use the Product Rule.
: Then differentiate again. Use the Quotient Rule, too.
: BTW, "natual log" is written "ln" - that's "LN".
Thank you for your help.
I tried it out using the product rule and quotient rule ,but I'm stuck again because what I got at the end seems a bit strange.
For this question y=4x^2In(x+5)
First I got
y'=8xLN(x+5)+ 4x^2 . 1/(x+5)
y'=8.1/(x+5) + 8x.-1(x+5)^-2
y'=8/(x+5) - 8x/(x+5)^2
But then in the second derivative,I got
y"=[(0(x+5)-8(1))/(x+5)^2] - [(8(x+5)^2 - 2(x+5).1)}/(x+5)^4]
Sorry the way I wrote it is so confusing. Please correct me if I'm wrong. Thank you very much!