Salut!
Aire carré: 60*60 = 3 600cm²
aire rectangle:
40 * (60-x)
2 400 - 40x
2 400 -40x = 3 600/4
2 400 -40x = 900
2 400 - 900 =40x
1500=40x
x= 1 500 /40
x = 37,5
AG = 60-37,5 =>22,5cm
