Question

( y )
( left[begin{array}{cc}1 & -5 6 & 7end{array}right]left[begin{array}{cc}2 & -3 4 & 8end{array}right]-2left[begin{array}{cc}1 & 0 0 & 1end{array}right] )
( Rightarrowleft[begin{array}{cc}1 times 2-5 times 4 & 1 times-3-5 times 8 6 times 2+7 times 4 & 6 times-3+7 times 8end{array}right]-left[begin{array}{cc}2 & 0 0 & 2end{array}right] )
( =left(begin{array}{cc}2-20 & -3-40 12+28 & -18+56end{array}right)-left(begin{array}{cc}2 & 0 0 & 2end{array}right) )
( Rightarrowleft[begin{array}{cc}-18 & -43 40 & 38end{array}right]-left[begin{array}{cc}2 & 0 0 & 2end{array}right] )
( Rightarrowleft(begin{array}{cc}-18-2 & -43-0 40-0 & 38-2end{array}right) )
( Rightarrow quadleft(begin{array}{cc}-20 & -43 -40 & 36end{array}right) )

# 1 - If A=. 704 8] -37 , Find AB - 21, where I is unit matrix of order 2.

Solution