Prove that $1280000401$ is Composite
You can say $1+x^2+x^7=1+x+x^2+(x^7-x)=1+x+x^2+x(x^3-1)(x^3+1)=(1+x+x^2)(1+x(x-1)(x^3+1))$
but your approach is a good one to find this. People have been very clever in finding things to try.
You can say $1+x^2+x^7=1+x+x^2+(x^7-x)=1+x+x^2+x(x^3-1)(x^3+1)=(1+x+x^2)(1+x(x-1)(x^3+1))$
but your approach is a good one to find this. People have been very clever in finding things to try.