Thực hiện phép tính:                  a) -1/5 + (-7/10)                                 b) 4 (-1/2)^2 + 1/2

  a) \(\frac{{ - 1}}{5} + \frac{{ - 7}}{{10}} = \frac{{ - 2}}{{10}} + \frac{{ - 7}}{{10}}\)

\( = \frac{{ - 9}}{{10}}\).               

b) \(4\,\,.\,\,{\left( {\frac{{ - 1}}{2}} \right)^2} + \frac{1}{2} = 4.\frac{1}{4} + \frac{1}{2}\)

                          \( = 1 + \frac{1}{2} = 1\frac{1}{2}\)