1.a = [( 7+n -11 )√5] : 2√5 = ( n -4 ) :2
2. BC² = AB²+AC² ; BC²=40²+30² =2500 ; BC=√2500 =50
3. h² = 3·12 =36cm² ; h = √36 cm = 6 cm
4. AM / ( AM+MB) = 2 /( 2+3) ; AM / AB = 2/5 ⇒ AN/AC = 2/5
5. ΔADE drept isoscel , CE =h = 6cm
aria = ( B+b) ·CE /2 = 24 · 6 /2 = 72 cm²
perim = 18 +4√2+6+4√2 = 24 +8√2 = 8( 3+√2) cm