Using the figure and the Pythagorean theorem, we can write two equations which both equal h^2 : ^2 =b^2 - (a-x)^2 and h^2 = d^2-x^2 . Set them equal to each other and solve for b^2 1. b^2 = d ^2-a^2-2ax
2. b^2=d^2-a^2+2ax
3. b^2 = (a-x) ^2 -d^2
4. . b^2=d^2-a^2-2ax