原式=(a2-b2+2b-1)/(a2-b2+a+b)=(a²-(b²-2b+1))/(a²-b²+a+b)=(a²-(b-1)²)/((a-b)(a+b)+a+b)=[a-(b-1)][a+(b-1)]/[(a-b+1)(a+b)]=[a-b+1)[a+b-1]/[(a-b+1)(a+b)]=(a+b-1)/(a+b)=(2009-...