a³-5a²b+3ab²-3b³-3ab²+5ab²-2a³
原式=﹙1-2﹚a³-5a²b+﹙3-3+5﹚ab²-3b³
=-a³-5a²b+5ab²-3b³
把a=-1,b=2代入上式得:
原式=﹙-1﹚²-5×﹙-1﹚²×2﹢5×﹙-1﹚×2-3×2²
=1-10-10-12
=-31
a³-5a²b+3ab²-3b³-3ab²+5ab²-2a³
原式=﹙1-2﹚a³-5a²b+﹙3-3+5﹚ab²-3b³
=-a³-5a²b+5ab²-3b³
把a=-1,b=2代入上式得:
原式=﹙-1﹚²-5×﹙-1﹚²×2﹢5×﹙-1﹚×2-3×2²
=1-10-10-12
=-31