Question 1050234
{{{6x-20/x=19}}}
{{{(6x^2-20-19x)/x=0}}}
{{{6x^2-19x-20=0}}}
{{{x=(19+-sqrt((-19)^2-4*6*(-20)))/(2*6)}}}
{{{x[1]=(19-sqrt(841))/12=(19-29)/12=-5/6}}}
{{{x[2]=(19+sqrt(841))/12=(19+29)/12=4}}}
Answer: f^-1(19)={{{-5/6}}}, f^-1(19)=4