a) Ta có :
\(\left(\frac{3}{7}+\frac{1}{2}\right)^2\)
= \(\left(\frac{6}{14}+\frac{7}{14}\right)^2\)
= \(\left(\frac{13}{14}\right)^2\)
= \(\frac{169}{196}\)
b)
\(\left(\frac{3}{4}-\frac{5}{6}\right)^2\)
= \(\left(\frac{18}{24}-\frac{20}{24}\right)^2\)
= \(\left(\frac{-1}{12}\right)^2\)
= \(\frac{1}{144}\)