a,2.(\(\dfrac{1}{4}\)+x)\(^3\)=(\(-\dfrac{27}{4}\))

b,(x+\(\dfrac{1}{2}\))\(^3\):3=\(\dfrac{-1}{81}\)

c,(\(\dfrac{2}{3}\)-x)\(^2\)=1:\(\dfrac{4}{9}\)

d,(2x-\(\dfrac{1}{5}\))\(^2\)+\(\dfrac{16}{25}\)=1

e,(\(\dfrac{2}{5}\)-3x)\(^2\)-\(\dfrac{1}{5}\)=\(\dfrac{4}{25}\)

bài 1: thực hiện phép tính 

a,\(\dfrac{15^3}{5^4}\)

b,\(\dfrac{21^3}{7^4}\)

c,\(\dfrac{6^6}{3^8}\)