Question

tim x : a, (\(\dfrac{1}{3}\)-\(\dfrac{1}{2}\))\(^{x-1}\)=\(\dfrac{1}{36}\)

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

Answer 1

a) \(\left(\dfrac{1}{3}-\dfrac{1}{2}\right)^{x-1}=\dfrac{1}{36}\) \(\Leftrightarrow\left(\dfrac{-1}{6}\right)^{x-1}=\dfrac{1}{36}\)

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

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

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

Answer 2

a) \(\left(\dfrac{1}{3}-\dfrac{1}{2}\right)^{x-1}=\dfrac{1}{36}\Leftrightarrow\left(-\dfrac{1}{6}\right)^{x-1}=\left(-\dfrac{1}{6}\right)^2\)

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

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

Giờ mới đúng thật nè

Answer 3

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

<=> (\(-\dfrac{1}{6}\))^x-1 = \(\dfrac{1}{36}\)

<=> (\(-\dfrac{1}{6}\))^x-1 = (\(-\dfrac{1}{6}\))²

<=> x - 1 = 2
<=> x = 3
@Nguyễn Thị Phương Thảo

Answer 4

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

<=> \(\dfrac{25}{5^x}=\dfrac{25}{3125}\)

<=> 5^x = 3125
<=> 5^x = 5⁵
<=> x = 5
@Nguyễn Thị Phương Thảo