Which of the given equations is not an explicit function of tt and is therefore useful when you don't know or don't need the time?

x$=$xi$+$vit$+12$at$2$x$=$xi$+$vit$+12$at$2$

v$=$vi$+$atv$=$vi$+$at

v$2=$v$2$i$+2$a$($x$$xi$)$