Question

Encontre o valor de x.

Answer 1

lei dos cossenos:
a² = b²+c² -2.b.c.(Cos A)
(2√7)² = x²+(2√3)² -2.x.2√3. (cos30)
28 = x²+12 -4x√3.(√3/2)
28 = x²+12 -6x
x²+12-6x -28 = 0
x² -6x -16 = 0
∆ = 36+64= 100 => √∆=10
x = -b+√∆/2a
x = 6+10/2 = 16/2 = 8 ✓