Question

∠ABC= 90°; BD⊥AC; BD=12 см; DC-AD=7 см Найти периметр треугольника ABC

Answer 1

BD^2 = AD*DC DC=AD+7
144 = AD*(AD+7) AD - x
144 = x^2+7x
X^2 + 7x -144 =0
D= 49 + 144*4 = 625
x = (-7+-25)/2
X = 9 x= -16 не удов усл.
AD = 9 DC = 16 AC = 9+16=25
BC^2 = 144 + 256 = 400 BC = 20
AB^2 = 625 - 400 = 225 AB=15
P= 15+20+25 = 60