(2a-3b)(3a-4b)=02a-3b=0 a=3b/23a-4b=0 a=4b/3a²-2ab/(a+b)(a-2b)=a(a-2b)/(a+b)(a-2b)=a/(a+b)(1)当 a=3b/2原式=(3b/2)/(3b/2+b)=(3b/2)/(5b/2)=3/5(2)当a=4b/3原式=(4b/3)/(4b/3+b)=(4b/3)/(7b/3)=4/7