Since you have the sum of the sides of a rectangle, 481, that is actually the square of the hypotenuse you get when the rectangle is split into two equal right triangles with a diagonal.
In short you can use the Pythagorean Theorem
Since
Length = w + 1
Width = w
We have
481 = w2 + (w + 1)2
481 = w2 + w2 + 2w +1
You can form a quadratic by moving everything over to one side
0 = 2w2 + 2w + 1 - 481
0 = 2w2 + 2w - 480
Divide both sides by 2
0 = w2 + w - 240
Factoring gives
0 = (w + 16)(w - 15)
Since the Width, w has to be positive
w = 15 is the only useful value
L = w +1 = 15 + 1 = 16
Length = 16
Width = 15
Checking against the sum of their squares
481 = 162 + 152
481 = 256 + 225
481 = 481
I hope you find this useful