原式=[(2.15+5.17)＋3.62]×[(2.15+5.17)＋8.5]－[3.62＋8.5＋(2.15+5.17)]×(2.15+5.17)
=(2.15+5.17)²+3.62×(2.15+5.17)+8.5×(2.15+5.17)+3.62×8.5-[3.62×(2.15+5.17)+8.5×(2.15+5.17)+(2.15+5.17)²]
=(2.15+5.17)²+3.62×(2.15+5.17)+8.5×(2.15+5.17)+3.62×8.5-3.62×(2.15+5.17)-8.5×(2.15+5.17)-(2.15+5.17)²
=3.62×8.5
=3.62×(9-0.5)
=3.62×9-3.62×0.5
=32.58-1.81
=30.77
或者：
令a=2.15+3.17
原式=(a＋3.62)×(a＋8.5)－(3.62＋8.5＋a)×a
=a²+3.62a+8.5a+3.62×8.5-(3.62a+8.5a+a²)
=a²+3.62a+8.5a+3.62×8.5-3.62a-8.5a-a²
=3.62×8.5
=3.62×(9-0.5)
=3.62×9-3.62×0.5
=32.58-1.81
=30.77