a) \(\left(\dfrac{3}{7}+\dfrac{1}{2}\right)^2=\left(\dfrac{13}{14}\right)^2=\dfrac{169}{196}\)
b) \(\left(\dfrac{3}{4}-\dfrac{5}{6}\right)^2=\left(\dfrac{-1}{12}\right)^2=\dfrac{1}{144}\)
c) \(\dfrac{5^4.20^4}{25^5.4^5}=\dfrac{\left(5.20\right)^4}{\left(25.4\right)^5}=\dfrac{100^4}{100^5}=\dfrac{1}{100}\)
d) \(\left(\dfrac{-10}{3}\right)^5.\left(\dfrac{-6}{5}\right)^4=\dfrac{-10^5}{3^5}.\dfrac{-6^4}{5^4}=\dfrac{-\left(2.5\right)^5.\left(3.2\right)^4}{3^5.5^4}=\dfrac{-29.5}{3}=-853\dfrac{1}{3}\)