turkey-yks 2015 Q30

turkey-yks · Other · lys1-math Laws of Logarithms Solve a Logarithmic Equation
Let k be a positive real number such that for the function
$$f ( x ) = \log _ { x } ( x - k )$$
we have $f ( 3 k ) = \frac { 2 } { 3 }$. What is k?
A) $\frac { 3 } { 8 }$
B) $\frac { 9 } { 8 }$
C) $\frac { 27 } { 8 }$
D) $\frac { 2 } { 9 }$
E) $\frac { 4 } { 9 }$
Let k be a positive real number such that for the function

$$f ( x ) = \log _ { x } ( x - k )$$

we have $f ( 3 k ) = \frac { 2 } { 3 }$. What is k?\\
A) $\frac { 3 } { 8 }$\\
B) $\frac { 9 } { 8 }$\\
C) $\frac { 27 } { 8 }$\\
D) $\frac { 2 } { 9 }$\\
E) $\frac { 4 } { 9 }$