What is the mathematical operation or theorem being applied in the calculations shown in the image?

Mathematical Operations and Theorems:

The image displays calculations that strongly suggest the application of the Pythagorean theorem ($$c^2 = a^2 + b^2$$) and possibly basic arithmetic operations like squaring and addition.

• The presence of $$c^2 = a^2 + b^2$$ explicitly points to the Pythagorean theorem, used for right-angled triangles.
• Calculations like $$90^2 5^2 + 3^2 + 5^2$$ and $$9^2 + 25^2$$ involve squaring numbers and adding them, which are fundamental steps in applying the Pythagorean theorem or other algebraic manipulations.
• There are also indications of simple arithmetic, such as $$c-16$$, which is a subtraction.