a|(3b-c) => 可设 c=3b-xa,b|(a-c) => 可设 c=a-yb=> 3b-xa=a-yb => (y+3)b=(x+1)a∵a,b是不同质数,∴b|(x+1),设x+1=mb则得y+3=ma => mc=m(a-yb)=ma-ymb=y+3-y(x+1)=3-xy若m=0,则得x=-1,y=-3,即此时c=a+3b又c|(2a-7b...