先化简再求值a²-2ab分之a²-2ab+9b²÷（a-2b分之2b²-a-2b

(a²-2ab+9b²)/(a²-2ab)÷(2b²-a-2b)/(a-2b)-1/a
=(a²-2ab+9b²)/a(a-2b)÷(2b²-a-2b)/(a-2b)-1/a
=(a²-2ab+9b²)/a(a-2b)×(a-2b)/(2b²-a-2b)-1/a
=(a²-2ab+9b²)/a(2b²-a-2b)-1/a
=(a²-2ab+9b²)/a(2b²-a-2b)-(2b²-a-2b)/a(2b²-a-2b)
=(a²-2ab+7b²+a+2b)/a(2b²-a-2b)
=(3²-2*3*1+7*1²+3+2*1)/3*(2*1²-3-2*1)
=15/(-9)
=-5/3
如果不懂,祝学习愉快!

没图的话都不知道到底是谁比谁，朋友没法做的