Chapter 2.5, Problem 4E

In Exercises 1–6, solve the equation Ax = b by using the LU factorization given for A. In Exercises 1 and 2, also solve Ax = b by ordinary row reduction.

4. $A=\left[\begin{array}{ccc}2& -2& 4\\ 1& -3& 1\\ 3& 7& 5\end{array}\right],b=\left[\begin{array}{c}0\\ -5\\ 7\end{array}\right]$

$A=\left[\begin{array}{ccc}1& 0& 0\\ 1/2& 1& 0\\ 3/2& -5& 1\end{array}\right]\left[\begin{array}{ccc}2& -2& 4\\ 0& -2& -1\\ 0& 0& -6\end{array}\right]$