hi. i need some help with a derivative question. i can get the answer and all but it takes a long time to do it. i need to find the instantaneous rate of change expression (derivative), and i MUST use the first principle. 1/(25x+4)^4 i can do this with the chain rule method quite easily. the first principle method takes forever as i use pascal's triangle to expand and the brackets and all. is there some sort of a quicker method where by substituting in some other variable or something. i really don't want to do ten or so of these that take 10 minutes to get through.