Bonjour,
aire du carré = x²
aire du rectangle = (x+1)(x+3) = x²+3x+x+3 = x²+4x+3
x²+4x+3 - x² = 4x + 3
si x=2, alors A = 4x+3 = 4(2)+3 = 11
si x=4,5 alors A = 4x+3 = 4(4,5)+3 = 21
