Hasil dari (a+b)(a+b)=

(a+b)(a+b) = (a+b)²
                  = a² + 2ab + b²

(a + b)(a + b)
= (a)(a) + (a)(b) + (b)(a) + (b)(b)
= a² + ab + ab + b²
= a² + 2ab + b²