Question

log x16=2
log x 16/81=4
log x5=-1

Answer 1

Log x16=2  
 log de base = x
x² = 16
x = √16
x = 4

log x 16/81=4
log de base x

x⁴ = 16/81                  ( 16 = 2x2x2x2 = 2⁴)
                                   (81 = 3x3x3x3 = 3⁴)
x = ⁴√16/81
x = ⁴√(2⁴/3⁴)
x = ⁴√(2/3)⁴     elimina a ⁴√(raiz a quarta) com o (⁴) fica
x = 2/3

log x5=-1

log de base x

x⁻¹ =  5                          ( atenção x⁻¹ = 1/x¹ = 1/x)

1
--- = 5
x¹

1
---= 5
x

1 = 5(x)
1 = 5x

5x = 1
x = 1/5