Question

已知X不等于1,(X-1)(X+1)=X^2-1,(X-1)(X^2+X+1)=X^3-1,(X-1)(X^3+X^2+

Answer 1

：(a-b)(a+b )=a^2-b^2 (a-b)(a²+ab+b² )=a^3-b^3 (a-b)(a³+a²b+ab²+b³)=a^4-b^4 2+2^2+2^3+.+2^n=2^(n+1)-2