This document proves the formula (a+b)2 = a2 + b2 + 2ab using both geometric and algebraic approaches. Geometrically, it represents a+b as a line segment and draws the squares and rectangles that make up (a+b)2. Algebraically, it expands (a+b)2 using the distributive property and collects like terms. Both methods demonstrate that (a+b)2 equals the sum of the squares of a and b plus twice their product.