(2a^3-1/6a^2b+3a)/(-1/3a)
=-6a²+2/3ab-9
(x-2)(x+2)-(x+1)(x-3)
=x²-4-x²+2x+3
=2x-1
(1-3y)(1+3y)(1+9y^2)
=(1-9y²)(1+9y²)
=1-81y⁴
(ab+1)^2-(ab-1)^2
=(ab+1+ab-1)(ab+1-ab+1)
=2ab×2
=4ab