E EmmaC New member Joined Jan 22, 2011 Messages 3 Jan 22, 2011 #1 How do you differentiate the following: ?(x)=15ln(7x)-5(x+15) for all x >0 & why is it concave? Normally I few problems with differentiation, but the (7x) and (x-15) has left me confused Regards, Emma
How do you differentiate the following: ?(x)=15ln(7x)-5(x+15) for all x >0 & why is it concave? Normally I few problems with differentiation, but the (7x) and (x-15) has left me confused Regards, Emma
G galactus Super Moderator Staff member Joined Sep 28, 2005 Messages 7,203 Jan 22, 2011 #2 The derivative of ln(7x) is 1/x, via the chain rule. The derivative of a constant is 0, the derivative of 5x is 5. So, the derivative is: \(\displaystyle \frac{15}{x}-5\)
The derivative of ln(7x) is 1/x, via the chain rule. The derivative of a constant is 0, the derivative of 5x is 5. So, the derivative is: \(\displaystyle \frac{15}{x}-5\)
