State whether the given equations are linear or nonlinear.

$($a$)(1-$ x$)$y$-4$xy$+5$y $=$ cos$($x$)$

$($b$)$x $-$

$1-$x$2$

$3$

$$x $+$ x $=0$

State whether the given equations are linear or nonlinear.

$($a$)(1-$x$)$y$^(\text{'}\text{'})-4$xy$^(\text{'})+5$y$=$cos$($x$)$

$($b$)$ x$^()-(1-($x$^()^(2))/(3))$x$^()+$x$=0$