解a/b=2/5∴(3a²-2ab+5b²)/(5a²-3ab+3b²)——分子分母除以b²=[3(a/b)²-2(a/b)+5]/[5(a/b)²-3(a/b)+3]=[3×(4/25)-2×(2/5)+5]/[5×(4/25)-3×(2/5)+3]=(12/25-4/5+5)/(4/5-6/5+3...