(1,0 điểm) Thực hiện phép tính: a) 16 1 4 : 5 3 − 6 1 4 : 5 3 + 2 2 . b) 1 15 : ( − 2 3 ) 2 + 2 15 . √ 81 16 − ( 2025 ) 0 .

a) \(16\frac{1}{4}:\frac{5}{3} - 6\frac{1}{4}:\frac{5}{3} + {2^2}\)

\( = 16\frac{1}{4}.\frac{3}{5} - 6\frac{1}{4}.\frac{3}{5} + 4\)

\( = \left( {16\frac{1}{4} - 6\frac{1}{4}} \right).\frac{3}{5} + 4\)

\( = 10.\frac{3}{5} + 4\)

\( = 2.3 + 4\)

\( = 6 + 4\)

\( = 10\).

b) \(\frac{1}{{15}}:{\left( { - \frac{2}{3}} \right)^2} + \frac{2}{{15}}.\sqrt {\frac{{81}}{{16}}} - {\left( {2025} \right)^0}\)

\( = \frac{1}{{15}}:\frac{4}{9} + \frac{2}{{15}}.\sqrt {{{\left( {\frac{9}{4}} \right)}^2}} - 1\)

\( = \frac{1}{{15}}.\frac{9}{4} + \frac{2}{{15}}.\frac{9}{4} - 1\)

\( = \left( {\frac{1}{{15}} + \frac{2}{{15}}} \right).\frac{9}{4} - 1\)

\( = \frac{3}{{15}}.\frac{9}{4} - 1\)

\( = \frac{1}{5}.\frac{9}{4} - 1\)

\( = \frac{9}{{20}} - 1\)

\( = - \frac{{11}}{{20}}\).