ITMC 2018 Grade 9 National Preliminary set01 Question 10

Observe $(a-b)(a+b)=a^2-b^2$, $(a-b)(a^2+ab+b^2)=a^3-b^3$, and $(a-b)(a^3+a^2b+ab^2+b^3)=a^4-b^4$. Find $(a-b)(a^5+a^4b+a^3b^2+a^2b^3+ab^4+b^5)$.