Taking 2nd, 3rd and 4th derivatives

[Cacophony]

Homework Statement

a) d^2/(dx^2): ln(x+1)
b) d^3/(dx^3): x^7 + 4x^6 - x^2
c) d^2/(dx^2): 1/(x + 1)
d) d^4/(dx^4): cos(2x)

Homework Equations

none

The Attempt at a Solution

Can someone tell me if these are right?

a)= -(1/(x + 1)^2)
b)=210x^4 + 480x^3
c)= (2/(x + 1)^3)
d)= 16cos(2x)

 

[tiny-tim]

Hi Cacophony!

(try using the X² button just above the Reply box )

Homework Statement

a) d^2/(dx^2): ln(x+1)
b) d^3/(dx^3): x^7 + 4x^6 - x^2
c) d^2/(dx^2): 1/(x + 1)
d) d^4/(dx^4): cos(2x)

Homework Equations

none

The Attempt at a Solution

Can someone tell me if these are right?

a)= -(1/(x + 1)^2)
b)=210x^4 + 480x^3
c)= (2/(x + 1)^3)
d)= 16cos(2x)

Yes, they're fine.