`= -(4/9)^7 : 4/7^2`
`= -(4/9)^(7-2)`
`= -(4/9)^5`
\(\left(-\dfrac{4}{9}\right)^7:\dfrac{16}{81}\)
\(=\left(-\dfrac{4}{9}\right)^7:\left(\dfrac{4}{9}\right)^2=\left(-\dfrac{4}{9}\right)^7:\left(-\dfrac{4}{9}\right)^2\)
\(=\left(-\dfrac{4}{9}\right)^{7-2}=\left(-\dfrac{4}{9}\right)^5\)
`(-4/9)^7 : 16/81 = (-4/9)^7 : (-4/9)^2 = (-4/9)^(7-2) = (-4/9)^5`