a)\(\left(\dfrac{a}{3}+4y\right)^2\)=\(\dfrac{a^2}{9}+\dfrac{8a}{3}+16y^2\)
b)\(\left(\dfrac{1}{x}-\dfrac{3}{y}\right)^2\)=\(\dfrac{1}{x^2}-\dfrac{6}{xy}+\dfrac{9}{y^2}\)
c)\(\left(\dfrac{x}{2}-\dfrac{yz}{6}\right)\left(\dfrac{x}{2}+\dfrac{yz}{6}\right)\)=\(\dfrac{x^2}{4}-\dfrac{\left(yz\right)^2}{36}\)
d)\(\left(x^2+\dfrac{2}{5}y\right)\left(x^2-\dfrac{2}{5}y\right)\)=x4-\(\dfrac{4}{10}y^2\)