The Erd\H{o}s-Selfridge and the Schinzel-Tijdeman theorems hold in $P{A}^{-}$

We show that “The product of consecutive integers is never a power” and several results by Schinzel and Tijdeman on the solutions of the equation $y^m=P(x)$, for $m>1$, $y>1$, and $P(x)$ a polynomial with rational coefficients and with at least two distinct zeros, hold in a weak fragment of Peano Arithmetic, $P{A}^{-}$, which lacks any kind of induction, and whose models are the positive cones of discretely ordered rings.