Determine the intervals on which f is increasing or decreasing and whether each of the critical points is a local maximum, minimum, or neither. f(x) = x^4 + 3x^3 + 3x^2 +1

Expert Answers

An illustration of the letter 'A' in a speech bubbles

Given `f(x)=x^4+3x^3+3x^2+1` :

To determine where the function is increasing or decreasing we look at the first derivative. If the first derivative is positive on aninterval then the function is increasing on the interval; if negative then the function is decreasing.

A critical point (where the derivative is zero) will be a maximum if the function is increasing from the left and decreasing to the right; a minimum if decreasing from the left and increasing to the right.




The only real zero is at x=0. Since the expression in the parantheses is always positive, we see that the derivative is negative for x<0, positive for x>0.

Thus the function decreases on `(-oo,0)` , increases on `(0,oo)` and the point (0,1) is a minimum.

The graph:

Approved by eNotes Editorial Team

Posted on

Soaring plane image

We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

  • 30,000+ book summaries
  • 20% study tools discount
  • Ad-free content
  • PDF downloads
  • 300,000+ answers
  • 5-star customer support
Start your 48-Hour Free Trial