20.解:(1)方程两边同乘(x 3)(x-3),得2(x 3) mx=5(x-3),解得x = ( 2 1 )/ ( 3 - m ).由题得 ( 2 1 )/ ( 3 - m ) < 0 , ( 2 1 )/ ( 3 - m ) ≠q ± 3,解得 m>3且x≠10.(2)3或10或-4 (2)解析:由(1)得2(x+3)+mx=5(x-3),即(3-m)x=21.由题意...