Question 474168
  <pre><font face = "Tohoma" size = 4 color = "indigo"><b> 
Hi,
{{{4k^2-81=0}}}
 (2k)^2 - 81 = 0
{{{2k = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
{{{2k = (-0 +- sqrt( 324))/(2) }}}
    2k = ± 9
     k = ± 4.5

CHECKING our Answers***
 4*(4.5)^2 - 81 = 0
 4*(-4.5)^2 - 81 = 0