1) Matrix A=[123115247], then the value of a31A31+a32A32+a33A33 is A) 1 B) 13 C) -1 D) -13 Answer: Option CExplanation: We have A=[123115247] a31=2, a32=4, a33= 7 and A31=[2315]=10−3=7 A32=−[1315]=−(5−3)=−2 A33=[1211]=1−2=−1 ∴ a31A31+a32A32+a33A33 = 2(7)+4(-2)+7(-1) =14-8-7=-1