Question 637395
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
f(x)=-x^2/288+18    V(0,18), parabola opening downward, height of beam is {{{18}}}
If f(x) = 0   &#8658;     x^2 = 18*288   and {{{x =sqrt(5184) =  72}}}
width of the beam is {{{72 + 72 = 144}}}    
{{{drawing(300,300,   -100, 100, -6, 20,  grid(1),
circle(72,0.3),
circle(-72, 0,0.3),
graph( 300, 300, -100, 100, -6, 20,0, -x^2/288+18))}}}