a) Thay x= -6; y=8;

ta có x(x-y)+y(x+y)= (-6).[(-6)-8]+8.[(-6)+8]

                             = (-6). -(14)+ 8. 2

                            = 100

b)

thay x=\(\dfrac{1}{2}\)

y=100;

ta có

\(\dfrac{1}{2}\)(\(^{\dfrac{1}{2}2}\)-100) - \(^{\dfrac{1}{2}2}\)(\(\dfrac{1}{2}\)+100) +100 (\(^{\dfrac{1}{2}2}\)-\(\dfrac{1}{2}\))

=\(\dfrac{-399}{8}\)- \(\dfrac{201}{8}\)+-25

=100