(a) Expand and simplify (a−b)(a2+ab+b2)(a - b)(a^2 + ab + b^2)(a−b)(a2+ab+b2).(b) Find the value of 20163+2015320162−20152.\dfrac{2016^3 + 2015^3}{2016^2 - 2015^2}.20162−2015220163+20153.