Differentiation question issues (1 Viewer)

[Talonus11]

Was just going through a past trial paper from my school, i got a different answer to the solutions at the back.
Question was: Find the second derivative of (3x² - 4)⁷
My answer was 1512x²(3x² - 4)⁵
The solutions answer was 42(3x² - 4)⁵(39x² - 4)
Just wanted to know if i did it wrong, or if it's the same answer, simply different form, if so, how did the solutions come to this?

 

[Slowness]

I got 1512x²(3x²-4)⁵


Numbers Fixed HEEEHAAAAA

 

[SeCKSiiMiNh]

p.s. How did you get those little numbers. Did you just copy and paste from word symbols thing or ... ??

just quote his post and you can see how he did it. DUH!

 

[Talonus11]

Okay, so i did it right, he just chain rule'd it differently. The numbers are done with (sup) and (/sup) (replace brackets with square brackets). Got it from the sticky up the top about rules and regulations.
eg. 3x squared is 3x(sup)2(/sup) but replacing round brackets with square brackets
Thanks

 

[Slowness]

Cheers

 

[dishab]

The answer is right

First differentiation u get ;- 42x (3x^2-40)^6

Then you use product rule:-
=42x.6(3x^2-4)^5 + 42 (3x^2-4)^6

= 42(3x^2-4)^5 (36x^2+3x^2-4)

= 42(3x^2-4)^5 (39x^2-4)

 

[hscishard]

Gotta hate how the first part misleads the second part.