Răspuns:
Explicație pas cu pas:
x² - 4x - a = 0
x₁+x₂ = 4/1 = 4
x₁x₂ = -a/1 = -a
x₁+x₂+3x₁x₂ = -2 =>
4-3a = -2 => 3a = 6 => a = 2
A(2 , 2) ; B(8 , 2) ; C(8 , 10) ; P = AB+AC+BC
AB² = (Xb - Xa)² + (Yb - Ya)²
AB² = (8-2)²+(2-2)² = 36 => AB = 6 u.m.
AC² = (8-2)²+(10-2)² = 36+84 = 100 => ac = 10 u.m.
BC² = (8²-8²)+(10-2)² = 64 => BC = 8 u.m.
P = 6 + 10 + 8 = > P =24 u.m.
