∵a+b=0
∴a=-b
2a+3b-4c的相反数=-(2a+3b-4c)=-(-2b+3b-4c)=4c-b
（2a+3b-4c)的2n次方（4c-2a-3b)2n+1次方
=(2a+3b-4c)²ⁿ[-(2a+3b-4c)]²ⁿ﹢¹
=-(2a+3b-4c)⁴ⁿ﹢¹