SOLUTION: I am trying to figure out how to figure the sum of a cube...125r^3+1. I am coming up with (x^2+5r+25r^2)(1+5r) but I am not sure it is correct. Can anyone help me? Thanks

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: I am trying to figure out how to figure the sum of a cube...125r^3+1. I am coming up with (x^2+5r+25r^2)(1+5r) but I am not sure it is correct. Can anyone help me? Thanks      Log On


   

Question 245464: I am trying to figure out how to figure the sum of a cube...125r^3+1. I am coming up with (x^2+5r+25r^2)(1+5r) but I am not sure it is correct. Can anyone help me? Thanks
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Factor:
125r%5E3%2B1 As you have pointed out, this is the sum of two cubes:
%285r%29%5E3%2B%281%29%5E3
The sum of two cubes is factored thus:
A%5E3%2BB%5E3+=+%28A%2BB%29%28A%5E2-AB%2BB%5E2%29 and here, A+=+5r, B+=+1, so...
125r%5E3%2B1+=+%285r%2B1%29%2825r%5E2-5r%2B1%29