Posted by **Jamie** on Tuesday, January 16, 2007 at 4:52pm.

a) y =ln(x-1) find dy/dx=?

b) y=3 ln x - ln (1/x) where x >0, dy/dx= ?

My teacher says the answers are a) (2x)/(x^2-1) and b) 4/x

I am not sure how you find the derivative when they involve ln. Could you please explain to me how to get these answers? I have a quiz on them soon so I just want to clearify how you would solve them. Thanks.

<<I am not sure how you find the derivative when they involve ln.>>

The derivative of ln x is 1/x. Use the "function of a function" rule when the log is of a function of x. For example:

y = ln (x-1)

Let u(x) = x-1

dy/dx = d (ln u)/du * du/dx = 1/u

= 1/(x-1)

You teacher is wrong on that one.

(2x)/(x^2-1)is the derivative of

ln (x^2 -1)

Perhaps you copied the problem wrong.

If y = 3 ln x - ln (1/x)

y = 3 ln x + ln x = 4 ln x

dy/dx = 4/x

## Answer this Question

## Related Questions

Introduction to Educational Theory - We have to analyze this situation: A ...

Early Child Ed. - Please check these questions and my answers: 1.For children ...

Math - I Don't Know What Is This Subject Called In English But It's About ...

calc - f(x)=6(sin(x))^x, find f'(1). and f(x)=3x^ln(x), find f'(9). i tried ...

math pre-calc h - It says which expressiion is equivalent to sec T + csc T / 1+...

SCIENCE - I have a homework pqage for kindergarten that says Petal Patterns. ...

Algebra - I am having trouble with finding the 1st and 3rd quartiles of a set of...

pre-calc - a farmer wants to make a rectangular enclosure using a wall as one ...

IQ - What is IQ??? Like when a teacher says this says it in your IQ. One time ...

Math (Pre-calc) - 1) F(x)= (X+2)/(X^2-4x-5) A) Find the domain (-00,-1)u(-1,5)u(...