The list of limit laws are here.
Constant Law limx->a k=k.
Identity Law limx->a x=a.
Sum Law limx->a f(x)+g(x) = limx->af(x) + limx->ag(x)
Difference Law limx->a f(x)-g(x) = limx->af(x) - limx->ag(x)
Constant Coefficient Law limx->a k*f(x) = klimx->af(x)
Multiplication Law limx->a f(x)*g(x) = limx->af(x) * limx->ag(x)