Bonjour,
1) aire ABCD = AB × BC = x(x+5) = x²+5x
aire EFGH = EF × FG = (x+1)(x+3) = x²+3x+x+3 = x²+4x+3
2) aire ABCD - aire EFGH = x²+5x - (x²+4x+3) = x² - x² + 5x - 4x - 3 = x - 3
3) aire ABCD > aire EFGH
⇒ aire ABCD - aire EFGH > 0
⇒ x - 3 > 0
⇒ x > 3
