a) $(2x+3)^3$
$=(2x)^3+3.(2x)^2.3+3.2x.3^2+3^3$
$=8x^3+36x^2+54x+8$
b) $\Bigg(\dfrac{1}{2}-y\Bigg)^3$
$=\dfrac{1}{8}-3.\dfrac{1}{4}.y+3.\dfrac{1}{2}.y^2-y^3$
$=\dfrac{1}{8}-\dfrac{3}{4}y+\dfrac{3}{2}y^2-y^3$
c) $\dfrac{1}{8}a^3+27b^3$
$=\Bigg(\dfrac{1}{2}a\Bigg)^3+(3b)^3$
$=\Bigg(\dfrac{1}{2}a+3b\Bigg)\Bigg(\dfrac{a^2}{4}-\dfrac{3ab}{2}+9b^2\Bigg)$
d) $\dfrac{1}{27}a^3-8b^3$
$=\Bigg(\dfrac{1}{3}a\Bigg)^3-(2b)^3$
$=\Bigg(\dfrac{1}{3}a-2b\Bigg)\Bigg(\dfrac{a^2}{9}+\dfrac{2ab}{3}+4b^2\Bigg)$
