Решение.

Применяем свойства степеней .

[tex]\bf 6)\ \ 0,4^0-(-0,25)^{-3}=1-\Big(-\dfrac{1}{4}\Big)^{-3}=1-(-4)^3=1-(-64)=1+64=65\\\\\\7)\ \ -(-2,5)^{-2}+\Big(-\dfrac{2}{5}\Big)^{-2}=-\Big(-\dfrac{25}{10}\Big)^{-2}+\Big(-\dfrac{5}{2}\Big)^2=-\Big(-\dfrac{10}{25}\Big)^2+\dfrac{5^2}{2^2}=\\\\\\=-\Big(-\dfrac{2}{5}\Big)^2+\dfrac{25}{4}=-\dfrac{2^2}{5^2}+\dfrac{25}{4}=-\dfrac{4}{25}+\dfrac{25}{4}=\dfrac{-4\cdot 4+25\cdot 25}{25\cdot 4}=\\\\\\=\dfrac{609}{100}=6,09[/tex]