The area is x(x+1) = 210 ft^2. Find x (the width) and then find (x+1) (the length).
x^2 + x - 210 = 0 can be solved using the quadratic formula, among other methods.
-1 plus or minus sqrt ( 1 - 4(1)(210) )
x = -------------------------------------------------------
2(1)
-1 plus or minus sqrt(841)
= --------------------------------------
2
Here, x has to be positive, since it's a measurement of length.
-1 + sqrt(841)
Thus, x = -------------------- (this is the width)
2
-1 + sqrt(841)
The length is 1 + ----------------------
2
