数据结构一元多项式相乘

A(x)=7-8x5+12x20-73x60+52x70-102x100+78x300
B(x)=4+15x7-82x30+73x50-36x70-46x120+29x400
C(x)=34-7x5-18x7-25x20-32x40+513x70-316x100-246x120-335x700
采用链式存储结构计算：D(x)=A(x)*B(x)-C(x)