Question

H(n)=n^3+2n; Find h(n+4)

Answer 1

`h(n)=n^3+2n\\\\h(n+4)=(n+4)^3+2(n+4)=n^3+3n^2\cdot4+3n\cdot4^2+4^3+2n+2\cdot4\\\\=n^3+12n^2+48n+64+2n+8=n^3+12n^2+50n+72`


`Used:\\\\(a+b)^3=a^3+3a^2b+3ab^2+b^3\\\\a\cdot(b+c)=ab+ac`