Explicație pas cu pas:
F(x)=x(x+4)(x+2)²-5 =>
F(x)=(x²+4x)(x²+4x+4)-5
Notam x²+4x=y<=>F=y(y+4)-5 =>
F=y²+4y-5=>F=y²+5y-y-5=>F=y(y+5)-1(y+5)=>F=(y+5)(y-2)
=>F(x)=(x²+4x+5)(x²+4x-2)
F(n)=(n²+4n+5)(n²+4n-2)
=> F(n) are ca divizori pe 1,n²+4n+5,n²+4n-2,F(n)
=> F(n) nr compus
