解：?$(1)$?當(dāng)?$x=5$?時(shí)，
代數(shù)式?$=2[\frac {m(5-4)}3-1]+\frac {m}5=2(\frac {m}3-1)+\frac {m}5$?
?$=\frac 23m-2+\frac {m}5$?
?$=\frac {13}{15}m-2$?
當(dāng)?$x=4$?時(shí)，
代數(shù)式?$=2[\frac {m(4-4)}3-1]+\frac {m}5=-2+\frac {m}5.$?
?$(2)$?由題意得對(duì)于?$x$?的任意取值，代數(shù)式的值都相等，則?$m=0$?，
此時(shí)代數(shù)式?$=-2.$?
