The perimeter of a rectangular garden is 268ft What dimensions must the garden have so that its area is more than 4480 sq ft?

For smallest dimension d, you want
  d(134-d) > 4480
  0 > d^2 - 134d + 4480
  9 > d^2 - 134d + 4489    (add 9 to complete the square)
  9 > (d-67)^2
  3 > d - 67 > -3    (the square root must be in this range)
  70 > d > 64

To get the desired area, the smallest dimension must be between 64 and 70 ft.