Найти f(A), еслиA^2-9A+20E A;=(6 2) ( 2 3 )

Решите задачу:

$A = \left[\begin{array}{cc}6&2\\2&3\\\end{array}\right], \\ A^2 = \left[\begin{array}{cc}36+4&12+6\\12+6&4+9\\\end{array}\right] = \left[\begin{array}{cc}40&18\\18&13\\\end{array}\right], \\ A^2 - 9A + 20E = \left[\begin{array}{cc}40 - 54 + 20&18-18\\18-18&13-27+20\\\end{array}\right] = \left[\begin{array}{cc}6&0\\0&6\\\end{array}\right] = 6E$