4(L+l+h)=24cm
=> L+l+h=6 cm ridicam la patrat
=> (L+l+h) ²=36 cm²
L²+l²+h²+2(L•l+L•h+l•h)=36cm²
2(L•l+L•h+l•h)=36cm²-( L²+l²+h²)
d=√(L²+l²+h²)=√14 cm
L²+l²+h²=14 cm²
2(L•l+L•h+l•h)=36cm²-14cm²=22cm²
At=2(L•l+L•h+l•h)=22cm²
