a) DC = 2x cm
FC = 3 cm
DC = DF + FC => DF + 3 = 2x cm
DF = 2x - 3 cm (latura patratului exprimata in functie de x)
b) aria patratului: latura² => aria AEFD = (2x-3)²
= (2x)² - (2·2x·3) + 3² = 4x² - 6x + 9 cm
c) aria AEFD = (2x-3)² = 49
49 este 7², deci (2x-3)²=7² =>
2x-3=7 => 2x = 10
x = 5
