Answer + the area of this rectangle is 210 ft^2. what is the length and width?

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