* $(a+b)^{3}$+$(a-b)^{3}$
= (a + b + a - b)[$(a+b)^{2}$ - (a + b)(a - b) + $(a-b)^{2}$
= (a + b - a + b)[$a^{2}$ + 2ab + $b^{2}$ - ($a^{2}$ - $b^{2}$) + $a^{2}$ - 2ab + $b^{2}$]
= 2a($a^{2}$ + 2ab + $b^{2}$ - $a^{2}$ + $b^{2}$ + $a^{2}$ - 2ab + $b^{2}$)
= 2a($a^{2}$ + $3b^{2}$)
* $(a+b)^{3}$-$(a-b)^{3}$
= [a + b - (a - b)][$(a+b)^{2}$ + (a + b)(a - b) + $(a-b)^{2}$
= (a + b - a + b)($a^{2}$ + 2ab + $b^{2}$ + $a^{2}$ - $b^{2}$ + $a^{2}$ - 2ab + $b^{2}$)
= 2b($3a^{2}$ + $b^{2}$)
