Chapter 5.5, Problem 18E

In Exercises 13–20, find an invertible matrix P and a matrix C of the form $\left[\begin{array}{cc}a& -b\\ b& a\end{array}\right]$ such that the given matrix has the form A = PCP⁻¹. For Exercises 13–16, use information from Exercises 1–4.

18. $\left[\begin{array}{cc}1& -1\\ .4& .6\end{array}\right]$