Find dy/dx at x = 2, if y =6u^2-11 and u = 3x^2 +2

[srizen]

the only part I am confused about is if i derive
y = 6u^2-11 first, then substitute u with 3x^2 +2.
or if i substitute u with 3x^2 +2, then expand/simplify, then derivate the entire question.

i got two answers.
using the first method f'(2) = 2016

and the second method f'(2) = 144

which method is right?

or am i just completely wrong.

 

[Ravi Mandavi]

2nd method is correct and its answer is 2016

 

[srizen]

2nd method is correct and its answer is 2016

alright, thanks for the clarification