Respuesta :

Write out the base-x expansion of [tex]101_x[/tex] :

[tex]101_x[/tex] = 1 • x² + 0 • x¹ + 1 • x

This number is equal to 17 (in base 10), so that

x² + 1 = 17

Solve this for x :

x² = 16

x = ±4

(Yes, negative bases are totally valid.)