The side of a rectangle can be calculated by rearranging the formula for computing area or perimeter given the other side length. Hence we have the following formulas for computing side given side .The formulas for computing side given are symmetric.
If we have only area and perimeter given of the rectangle and want to compute one of the sides, for instance side , we possibly have two solutions. We rearrange the formulasby plugging in from the area formula into the perimeter formula. This then leads to the quadratic equationfor which we can have two solutions.