The problem involves finding an algebraic expression for a sequence defined by the terms -15, 30, 90, and -360. The original poster seeks to understand the pattern governing the sequence.
Some participants have identified a potential recursive relationship among the terms and are exploring how to express this in algebraic form. There is ongoing inquiry into the nature of the sequence and the signs of the terms, but no consensus has been reached on a definitive expression.
The original poster has expressed uncertainty about the problem, indicating a lack of initial ideas. The discussion includes considerations of the sequence's structure and the implications of the term number on the calculations.
That's what I want to find out. It does not necessarily have to be multiplication only.DivisionByZro said:What do you multiply each term by to get the next?
HallsofIvy said:Are you saying that you have a sequence, [itex]a_1= -15[/itex], [itex]a_2= 30[/itex], [itex]a_3= 90[/itex], and [itex]a_4= -360[/itex]?
Well, I notice that 30= 2*15, 90= 3*30, and 360= 4*90. That is, [itex]a_n= n*a_{n-1}[/itex]. Also, the signs are -, +, +, -. You should be able to find a power of -1, in terms of n, that will give that.