a)
(A+B) does not exist, since matrices are of different sizes (2x3 and 3x2)
AB=(82−102−5)⎝⎛−1317−25⎠⎞=(−8−3+2−2−556+2+1014−25)=(−9−768−11)
b)
(AB)C=(−9−768−11)(2315)=(−18+204−14−33−9+340−7−55)=(186−47331−62)
BC=⎝⎛−1317−25⎠⎞(2315)=⎝⎛−2+216−62+15−1+353−101+25⎠⎞=⎝⎛1901734−726⎠⎞
A(BC)=(82−102−5)⎝⎛1901734−726⎠⎞=(152+3438−85272+7+5268−130)=
=(186−47331−62)
c)
for C-1:
C∗=(5−1−32) , C∗T=(5−3−12)
∣C∣=10−3=7
C−1=∣C∣C∗T==71(5−3−12)
C−1A=71(5−3−12)(82−102−5)=71(40−2−24+4−5310+5−6−10)=
=71(38−20−5315−16)
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