The width of a rectangle is 3 less than twice its length. If the area of the rectangle is 78 $\displaystyle \text{cm}^{{2}}$, what is the length of the diagonal?

The length of the diagonal is cm.

Give your answer to 2 decimal places.

Note: Since you are looking for the diagonal you will want to use the pythagorean theorem, $\displaystyle {a}^{{2}}+{b}^{{2}}={c}^{{2}}$