If a function f is defined by f(x)= 2x/(x-1) for all non zero numbers x. If f(a) = 4 and f(ab) = 6 then b= ? Pick one:
A) 3/2  B) 1/2  C) 7/2  D) 3/4  E) 1/4
Given that f(x) =2x/(x-1) and f(a) = 4, then f(a) =2a/(a-1)=4 ===&gt; 2a = 4a -4 =&gt; a =2, then backsolve using the answer choices:   f(ab) = f(2b) = 6   A) 3/2 ===&gt; f(2*3/2) = f(3) = 2*3/(3-1) = 6/ 2= 
<gadget id="calculator">6/ 2</gadget>
<output>3</output>
3   B) 1/2===&gt; f((2*1/2) = f(1) = 2*1/(1-1) = undefined   C) 7/2 ===&gt; f(2*7/2) = f(7) = 2*7/(7-1) = 14/6 = 7/3   3/4) 3/4 ===&gt; f(2*3/4) = f(3/2) (2*3/2)/(3/2-1) = 3/(1/2)= 
<gadget id="calculator">3/(1/2)</gadget>
<output>6</output>
6 WINS   E) 1/4===&gt; f(2*-1/4) = f(1/2) = (2*1/2)/(1/2-1) = 1/-1/2 = -2   Answer: 3/4
<result>D</result>
If a function f is defined by f(x)= 2x/(x-1) for all non zero numbers x. If f(a) = 4 and f(ab) = 6 then b= ?