log1/2[a^2x+2(ab)^x-3b^2x+1]＜0 ==>a^2x+2(ab)^x-3b^2x+1>1 ==> a^2x+2(ab)^x-3b^2x>0化为((a/b)^x+3)((a/b)^x-1)>0 所以（a/b)^x>1=(a/b)^0a>b时 ,x>0;a