Let $ B=\{(1,0,1), \ (1,1,-1) , \ (2,0,1) \} \ $ be a basis for $ \ \mathbb{R}^3 \ $ and let $ \ v=(-9,1,-8) \ $. 

Find $ \ [v]\_B \ $ and interpret what it means.

**Answer:**

My question is if the transformation is not given then how to find the matrix $ \ [v]\_B \ $ ?