Is $PQ$PQ, the product of $P_{4\times2}$P4×2 and $Q_{2\times3}$Q2×3, defined?
No
Yes
What are its dimensions?
$\editable{}$ × $\editable{}$
Is $R$R$S$S, the product of $R_{5\times4}$R5×4 and $S_{3\times4}$S3×4, defined?
Is $S$S$R$R, the product of $R_{5\times3}$R5×3 and $S_{4\times5}$S4×5, defined?
Consider $A$A$=$= | $-7$−7 | $-3$−3 | $-1$−1 | . | ||
$5$5 | $7$7 | $-6$−6 |
If $A$A is to be multiplied by $B$B, a column matrix, what are the dimensions of $B$B?