(1,0 điểm) Thực hiện phép tính: a) 3 5 . 7 9 + 3 5 . 2 9 ; b) ( 1 2 − 2 3 ) 2 + 1 2 3 : | − 0 , 75 | − √ 1 16 .

a) \(\frac{3}{5}.\frac{7}{9} + \frac{3}{5}.\frac{2}{9}\)

\( = \frac{3}{5}.\left( {\frac{7}{9} + \frac{2}{9}} \right)\)

\( = \frac{3}{5}.1 = \frac{3}{5}.\)

b) \({\left( {\frac{1}{2} - \frac{2}{3}} \right)^2} + 1\frac{2}{3}:\left| { - 0,75} \right| - \sqrt {\frac{1}{{16}}} \)

\( = {\left( { - \frac{1}{6}} \right)^2} + \frac{5}{3}:0,75 - \frac{1}{4}\)

\( = \frac{1}{{36}} + \frac{5}{3}:\frac{3}{4} - \frac{1}{4}\)

\( = \frac{1}{{36}} + \frac{5}{3}.\frac{4}{3} - \frac{1}{4}\)

\( = \frac{1}{{36}} + \frac{{20}}{9} - \frac{1}{4}\)

\( = \frac{1}{{36}} + \frac{{80}}{{36}} - \frac{9}{{36}} = \frac{{72}}{{36}} = 2\).