<span>difference of f squared and g = (f^2 - g) </span>4 times the difference of f squared and g = 4 x (f^2 - g<span>) </span><span>sum of f squared and 2g = (f^2 + 2g)
</span>4 times the difference of f squared and g, increased by the sum of f squared and 2g = 4 x (f^2 - g) + (f^2 + 2g<span>)</span>