Question 913834
{{{ 1-x^-1-20x^-2=0}}}

{{{ 1-1/x-20(1/x^2)=0}}}

{{{ 1x^2/x^2-1x/x^2-20/x^2=0}}}

{{{ (x^2-x-20)/x^2=0}}}

{{{ (x^2-x-20)=0*x^2}}}

{{{ x^2-x-20=0}}}


{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 


{{{x = (-(-1) +- sqrt( (-1)^2-4*1*(-20)) )/(2*1) }}} 


{{{x = (1 +- sqrt( 1+80) ))/2 }}} 


{{{x = (1 +- sqrt( 81) ))/2 }}} 


{{{x = (1 +- 9 )/2 }}} 

solutions:


{{{x = (1 + 9 )/2 }}} 

{{{x = (1 + 9 )/2 }}}

{{{x = 10/2 }}}

{{{x = 5 }}}

or

{{{x = (1 - 9 )/2 }}} 

{{{x = (1- 9 )/2 }}}

{{{x = -8/2 }}}

{{{x = -4 }}}


{{{ graph( 600, 600, -10, 10, -10, 10, 1-x^-1-20x^-2) }}}