Chapter 8 - Section 8.1 - The Square Root Property and Completing the Square - Exercise Set - Page 595: 88

The required length of the supporting wire is $c= 70\sqrt{2} ft$.

Using the Pythagorean theorem $c^2 = a^2 + b^2$, the length of the wire can be obtained by setting up an equation for the hypotenuse, $c$: $a = 70ft$ $b = 70ft$ $c^2 = a^2 + b^2$ $c^2 = 70^2 + 70^2$ $c^2 = 9800$ $c= \sqrt{9800}$ $c= \sqrt{(4900·2)}$ $c= 70\sqrt{2} ft$