Please fastly!!!

3) Characterize in general terms (and with your own words) the worst-case scenario in the complexity analysis. 4) How (in terms of which quantity) can one find out the complexity of the general recursive processes? 5) What is the complexity of the Fast Fourier Transform algorithm? How (by what mechanism) is it achieved? 6) Consider a naive algorithm of the matrix multiplication in the linear algebra. "Naive" means that we simply multiply and add corresponding terms in the rows and columns of the matrices. What is its complexity