Question

Jika x^1/3+x^-1/3=4
Maka nilai x+1/x adalah
a.32,
b.42,
c.52,
d.60,
e.62

Answer 1

Ingat:
(a + b)³ = a³ + b³ + 3ab(a + b)

(x^1/3 + x^-1/3)³ = x + x⁻¹ + 3x^(1/3 - 1/3) (x^1/3 + x^-1/3)
            64         = x + x⁻¹ + 3(4)
              x + x⁻¹ = 64 - 12 = 52
              

Answer 2

 64         = x + x⁻¹ + 3(4) x + x⁻¹ + 3(4)
              x + x⁻¹ = 64 - 12 = 52