Question 23299
Perimeter = 2l+2w = 300
    l+w =150
      w = 150-l
Area =lw
     =l(150-l)
     =150l-l^2
This is a quadratic in "l" where 
a=-1, b=150, c=0
*[invoke quadratic "x",-1,150,0]
The maximum is at l=-b/2a = 150/2=75
Maximum area occurs when l=75 and w=75

Cheers,
stan H.