posted by Anonymous .
There is no function here. Is there an equal sign somewhere here? A function? What is your question?
presumably you meant
y = 6x - 4cos(3x)
y' = 6 + 12sin(3x)
y'' = 36cos(3x)
Now, I'm sure you know all about 1st and second derivatives and how they relate to critical numbers:
y has a max/min where y' = 0 and y'' not zero
y has an inflection point where y'' = 0
y is increasing where y' >. 0
y is concave up when y'' > 0
No go plug and chug