Which visual model shows a(a+b) by combining one a² square and one ab rectangle?

Correct answer: A rectangle with length (a+b) and breadth a

The direct answer is A. A rectangle with length a+b and breadth a has area a(a+b). If the length is split into parts a and b, the rectangle is divided into an a by a square and an a by b rectangle. Their areas are a² and ab, so the total is a²+ab. Factoring out a gives a(a+b), exactly as required. B represents a much larger square with area (a+b)² and would contain four parts, not just a² and ab. C has area b(a−b), which is a different expression and uses the wrong common dimension. D has side ab, so its area is (ab)², not a(a+b). Thus A is the only model whose dimensions and partition match. Memory cue: a common factor a means one side of the rectangle is a; the other side is the sum a+b.