I think you forgot to finish: you still have to do the 4x part inside. You can see an explanation here from the Math Forum site. The Purplemath writer did something in alt groups back in 1999 here. Where PM talks about "the rest", that's the same as where MF talks about "BLOB".Q: Let f(x)=20x-10sin(4x) for 0<=x<=pi/2
Find the largest interval(s) over which the function f is increasing or decreasing.
I tried to solve this: