bonjour

rectangle 1 = 2 a ( a + 3 ) = 2 a² + 6 a

rectangle  2 =  2 a

rectangle  3 = 2 a * 2 a = 4 a²

somme  =  2 a² + 6 a + 2 a + 4 a² = 6 a² + 8 a

(6 a² + 8 a ) : 2 a

= 3 a² + 4