原式=(a的n次方)³×(b³)³×a²×(b的2n-7次方)-[a的2(n+1)次方]×b²×(a的n次方)×(b的2n次方)
=(a的3n次方)×(b的9次方)×a²×(b的2n-7)次方-[a的2(n+1)+n次方]×(b的2n+2次方)
=(a的3n+2次方)×(b的9+2n-7次方)-(a的3n+2次方)×(b的2n+2次方)
=(a的3n+2次方)×(b的2n+2次方)-(a的3n+2次方)×(b的2n+2次方)
=0