# 2 chain rules problems

1. Sep 27, 2011

### bblair3

For some reason I am struggling with these problems. I am lost as a goose trying to fly south for the winter!

1. The problem statement, all variables and given/known data

9^(5-x2)
and
another derivative problem using chain rule
r/square root of the whole term r^2+5

2. Relevant equations

1st equation= d/dx= a^x ln a
2nd equation=

3. The attempt at a solution

1st one= -9^(5-x^2) 2x log (9)

2nd one= i am stuck at square root of (r^2 +5) + square rt (r^2+5) -r^2 all divided by sq root of (r^2+5) all divided by (r^2 +5)^2

any help would be greatly appreciated!!!

2. Sep 27, 2011

### SammyS

Staff Emeritus
1st one looks right.

2nd one: Write using a fractional exponent for square root.

r/(r2+5)1/2 = r(r2+5)-1/2. Take the derivative of this.

3. Sep 27, 2011

### bblair3

apparently webassign does not like the answer -9^(5-x^2)2x log (9)

2. 5/(r^2+5)^3/2

4. Sep 27, 2011

### bblair3

the second is right :) thanks....now to figure out what is going on with the first one

5. Sep 27, 2011

### SammyS

Staff Emeritus
Does WebAssign want log or does it want ln for the log base e ?

6. Sep 27, 2011

### bblair3

i will try ln base e

7. Sep 27, 2011

### bblair3

it indeed up being ln
thanks for your help Sammy S :)