Please write clearly, thank you very much

Let AMnn(F). Prove the following statements. (a) If {v1,,vn} is a basis for Fn that triangularizes LA, then the matrix Q=(v1vn)Mnn(F) is invertible, and Q1AQ is upper triangular. (b) Conversely, if QMnn(F) is an invertible matrix such that Q1AQ is upper triangular, then the column vectors of Q form a basis for Fn that triangularizes LA