Đề bài

Tính một cách hợp lí:

a) $\dfrac{{ - 5}}{7}.\dfrac{2}{{11}} + \dfrac{{ - 5}}{7}.\dfrac{9}{{11}} + \dfrac{5}{7}$;

b) $\left[ {\left( {\dfrac{{ - 3}}{8} + \dfrac{{11}}{{23}}} \right):\dfrac{5}{9} + \left( {\dfrac{{ - 5}}{8} + \dfrac{{12}}{{23}}} \right):\dfrac{5}{9}} \right].\dfrac{{ - 11}}{{325}}$;

c*) $\dfrac{{{{15}^5}}}{{{5^5}}} - {( - 0,25)^2}{.4^2}$;

d*) $- \dfrac{{{2^{15}}{{.9}^4}}}{{{6^6}{{.8}^3}}} + 0,75.\dfrac{{ - 1}}{2} + 0,375$.