diketahui matrik-matrik : A= [ 2 1 ] , B= [ -1 2 ] , C= [ α -3 ] [ 3 4 ] [ 5 6 ] [ -7 -8 ] Jika determinan dari A-2B=C, maka nilai α

[tex]\det(A-2B)=\det(C) \\ \left|\begin{array}{cc}2&1\\3&4\end{array}+\begin{array}{cc}-2&4\\10&12\end{array}\right|=\left|\begin{array}{ccc}a&-3\\-7&-8\end{array}\right| \\ \left|\begin{array}{ccc}0&5\\13&16\end{array}\right|=\left|\begin{array}{ccc}a&-3\\-7&-8\end{array}\right| \\ \\ 0.16-13.5=a(-8)-(-7)(-3) \\ -65=-8a-21 \\ 8a+21=65 \\ 8a = 44 \\ a=10,5[/tex]
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