You can
put this solution on YOUR website!x = width
3x = length
Area = Length X Width, so

, which is your quadratic equation in standard form.
Factors to:
So,

or

. The negative result doesn't make much sense in terms of the dimensions of a rectangle, so we can exclude that root. The width of the rectangle is therefore 5 meters, and the length is 3 * 5 =15 meters.