Find the sum to n terms of this series: 1 -y +y^2 -y^3 ... I have figured that a=(-1)^n+1. r=-y.
Follow Math Help Forum on Facebook and Google+
You are correct in saying that r=-y, but you're overcomplicating the other part: a is just the first term in this series. In this case, a = 1. Now you just need to substitute the values into the formula.
That works but it isn't the answer in the book. It is: 1+((-1)^n+1) * y^n divided by 1+y.
Hmm...have you posted the question correctly? I can't see any error in my logic.
You and the book are correct. The answer in the book confused me. They must have decided to take the answer a step further.
You are considering . And the first term of your series is :a= 1. so the sum of the geometric series would be given by: try plugging in the values now
I've already done that after the first post by Quacky.
I think the textbook is either misprinted or has found some other values which also work, but I don't believe my calculation is incorrect.
Originally Posted by Stuck Man Find the sum to n terms of this series: 1 -y +y^2 -y^3 ... I have figured that a=(-1)^n+1. r=-y.
Thats more work than necessary. You don't need to have loads of steps to produce the coefficient of -1 or 1.
Originally Posted by Stuck Man Thats more work than necessary. You don't need to have loads of steps to produce the coefficient of -1 or 1. The steps are only for clarity.
View Tag Cloud