\(a)-12:(\dfrac{3}{4}:\dfrac{5}{6})^2=-12:(\dfrac{9}{12}:\dfrac{25}{36})=-12:\dfrac{54}{10}=\dfrac{54}{-120}=\dfrac{9}{20}\)
\(b)\dfrac{1}{3}-1=\dfrac{1}{3}-\dfrac{3}{3}=\dfrac{-2}{3}\)
\(\dfrac{4}{15}x=-\dfrac{3}{5}=x=\dfrac{4}{15}:\dfrac{3}{5}=x=\dfrac{20}{45}=\dfrac{4}{9}\)
\(\dfrac{-2}{3}<\dfrac{4}{9}\)
\(c)\dfrac{-3}{81}^x=-27=\dfrac{-3}{81}^7=-27\)
\(s)-(x-1)^2=-25<=>[-(x-1)^2=-25<=>[x=5\)
còn lại tự làm nha
\(a,-12\div\left(\dfrac{3}{4}\div\dfrac{5}{6}\right)^2=-12\div\left(\dfrac{9}{10}\right)^2=-12\div\dfrac{81}{100}=-\dfrac{400}{27}\)
\(b,\dfrac{1}{3}-1=-\dfrac{2}{3}\)
\(\dfrac{4}{15}x=-\dfrac{3}{5}\)
\(x=\dfrac{4}{15}\div-\dfrac{3}{5}\)
\(x=-\dfrac{4}{9}\)
\(-\dfrac{2}{3}< -\dfrac{4}{9}\)
\(\Rightarrow\dfrac{1}{3}-1< \dfrac{4}{15}x=-\dfrac{3}{5}\)
\(c,\dfrac{\left(-3\right)^x}{81}=-27\)
\(\left(-3\right)^x=-27.81\)
\(\left(-3\right)^x=-2187\)
\(\left(-3\right)^x=-3^7\)
\(x=7\)
\(s,-\left(x-1\right)^2=-25\)
\(-\left(x-1\right)^2=-\left(-5\right)^2\)
\(x=5+1\)
\(x=6\)
\(e,2^{x-1}=16\)
\(2^{x-1}=2^4\)
\(x=4+1\)
\(x=5\)
\(g,2\dfrac{2}{3}\div x=1\dfrac{7}{9}\div2\dfrac{2}{3}\)
\(\dfrac{8}{3}\div x=\dfrac{16}{9}\div\dfrac{8}{3}\)
\(\dfrac{8}{3}\div x=\dfrac{2}{3}\)
\(x=\dfrac{8}{3}\div\dfrac{2}{3}\)
\(x=4\)
