Chapter $4$ Linear Mudels and Malrix Algehra. $73$

$2.$ Calculate: $($a$)Ab$

$($b$)A1b$

$($c$)x^{\text{'}}|A|$

$($d$)x^{\text{'}}A$

Does the insertion of $l$ in $($b$)$ affect the result in $($a$)?$ Does the deletion of $l$ in $($d$)$ affect. the result in $($c$)?$