Using Eq. (4), apply the singularity test to the matrices in Exercises 13-16. Show that there is no real scalar > such that A-7 is singular. [Note: Complex eigenvalues are discussed in Section 4.6.] -2-1 13. A = -[ 14. A = 3-2 5-3 5 2 15. Am -[2-2] 16. A [H] 17. Consider the (2 x 2) symmetric matrix a b ^-[88] b d Show that there are always real scalars à such that A-AI is singular. [Hint: Use the quadratic formula for the roots of Eq. (5).] 18. Consider the (2 x 2) matrix A given by a b ^ = [-% %] · ·