解0.49x²-0.04y²=0.01(49x²-4y²)=0.01(7x+2y)(7x-2y)-4a²b²+4ab-1=-(4ab²-4ab+1)=-(2ab-1)²-3a³x+12ax³=-3ax(a²-4x²)=-3ax(a+2x)(a-2x)m³n-2m
...