$6.($a$)$ What is wrong with the following equation?

x$48$x$2+16$

x$24=$ x$24$

$($b$)$ In view of part $($a$),$ explain why the equation

lim

x$2$

x$48$x$2+16$

x$24=$ lim

x$2($x$24)$

is correct.