If A\left[\begin{array}{cc}3 & 7 \ 2 & 4]\end{array}, {\B}=\left[\begin{array}{cc}0 & 2 \ 5 & 3]\end{array} and {\C}=\left[\begin{array}{cc}1 & -5 \ -4 & 6]\end{array} Find {\AB}-5 {\C} .

ICSE Class X Math 2015 Solved Paper - Question 46

Question : 46 of 52

Marks: +1, -0

A{[\table 3 , 7 ; 2 , 4]}, {\B}={[\table 0 , 2 ; 5 , 3]}

and

{\C}={[\table 1 , -5 ; -4 , 6]}

Find

{\AB}-5 {\C}

Solution:

\;\text " Given : "\;

{\A}\;={[\table 3 , 7 ; 2 , 4 ]}, {\B}={[\table 0 , 2 ; 5 , 3 ]}, {\C}

={[\table 1 , -5 ; -4 , 6 ]}

{\AB}\;={[\table 3 , 7 ; 2 , 4 ]}{[\table 0 , 2 ; 5 , 3 ]}

\;={[\table 0+35 , 6+21 ; 0+20 , 4+12 ]}={[\table 35 , 27 ; 20 , 16 ]}

5 {\C}\;=5{[\table 1 , -5 ; -4 , 6 ]}

\;={[\table 5 , -25 ; -20 , 30 ]}

{\AB}-5 {\C}\;={[\table 35 , 27 ; 20 , 16 ]}-{[\table 5 , -25 ; -20,30 ]}

=[\table 30 , 52 ; 40 , -14]

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