30. Let f(x)= x^4-8x^2. Using the first derivative, find all the intervals where the function is increasing and all the intervals where it is decreasing. (10 points) 31. Using the same function from problem 30, use the first derivative to find all local extrema. (10 points) 32. Using the same function from problem 30, use the second derivative to find all local extrema. (10 points)