Question

What is the value of d21+d22+d23 given the matrix equation below?

Answer 1

Answer:b

Step-by-step explanation:

Answer 2

Keeping in mind that the element labeling is row,column, thus 2,1 simply means the 2nd row and 1st column, thus

$\bf \stackrel{D}{ \begin{bmatrix} \boxed{}&\boxed{}&\boxed{}\\ d_{2,1}&d_{2,2}&d_{2,3}\\ \boxed{}&\boxed{}&\boxed{} \end{bmatrix}}+ \begin{bmatrix} 1&0&1\\-3&9&-7\\-20&2&4 \end{bmatrix}= \begin{bmatrix} 9&-3&2\\ 8&-1&0\\11&15&3 \end{bmatrix} \\\\\\ d_{2,1}+(-3)=8\implies \boxed{d_{2,1}=11} \\\\\\ d_{2,2}+9=-1\implies \boxed{d_{2,2}=-10} \\\\\\ d_{2,3}+(-7)=0\implies \boxed{d_{2,3}=7}\\\\ -------------------------------\\\\ 11+(-10)+7\implies 8$