解:x^5-1=(x-1)(x^4+x^3+x^2+x+1)
x^5+1=(x+1)(x^4-x^3+x^2-x+1);
做题应该记住:x^n+1=(x+1)[x^(n-1)-x^(n-2)+...+(-1)^(k+1)x^(n-k)+...+(-1)^(n+1)];
x^n-1=(x-1)[x^(n-1)+x^(n-2)+...+1];n∈N*。
x^5+1
=x^5+x^4-x^4+1
=x^4(x+1)-(x^4-1)
=x^4(x+1)-(x^2+1)(x+1)(x-1)
=(x+1)[x^4-(x^2+1)(x-1)]
=(x+1)[x^4-x^3+x^2-x+1)
=(x+1)(x^4-x^3+x^2-x+1)