解?$：(3)$?原式?$=(a ·b) \sqrt {b ·a}-(a ·a) \sqrt {b ·b} +(b ·b) \sqrt {a ·a}-(b ·a) \sqrt {a ·b} $?
?$=a b \sqrt {a b}-a^2 \sqrt {b^2}+b^2 \sqrt {a^2} -a b \sqrt {a b} $?
?$=a b \sqrt {a b}-a^2\ \mathrm +a b^2-a b \sqrt {a b} $?
?$=-a^2\ \mathrm +a b^2$?
?$(2)$?原式?$=3\ \mathrm {m^2} \sqrt {m}+2\ \mathrm {m^2} \sqrt {m}-2\ \mathrm {m^2} \sqrt {m} $?
?$=3\ \mathrm {m^2} \sqrt {m}$?
