Question

tim x ,

a, (1/3-1/2)^x-1=1/36

b,\(\dfrac{25}{5^x}\)= \(\dfrac{1}{125}\)

Answer 1

a) \(\left(\dfrac{1}{3}-\dfrac{1}{2}\right)^x-1=\dfrac{1}{36}\)

\(\Rightarrow\left(\dfrac{1}{6}\right)^x=1\dfrac{1}{36}\)

\(\Rightarrow x=2\)

b) \(\dfrac{25}{5x}=\dfrac{1}{125}\)

\(\Rightarrow25\cdot125=5x\)

\(\Rightarrow5^2\cdot5^3=5^x\)

\(\Rightarrow x=5\)

Answer 2

Bn Đời về cơ bản là buồn... cười!!! nhìn sai đề ở ý a .

a) \(\left(\dfrac{1}{3}-\dfrac{1}{2}\right)^{x-1}=\dfrac{1}{36}\)

\(\Leftrightarrow\left(-\dfrac{1}{6}\right)^{x-1}=\dfrac{1}{36}\)

\(\Leftrightarrow\left(-\dfrac{1}{6}\right)^{x-1}=\dfrac{1}{6}^2\)

\(\Leftrightarrow x-1=2\Rightarrow x=3\)

b) \(\dfrac{25}{5^x}=\dfrac{1}{125}\Leftrightarrow\dfrac{25}{5^x}=\dfrac{25}{3125}\Leftrightarrow\dfrac{25}{5^x}=\dfrac{25}{5^5}\Rightarrow x=5\)