Lemma. Assuming that:

Then

\begin{array}{l} ψ (x_{1}, \dots, x_{m}) & : = φ (G_{1} (x_{1}, \dots, x_{m}), \dots, G_{n} (x_{1}, \dots, x_{m})) \\ H (x_{1}, \dots, x_{m}) & : = F (G_{1} (x_{1}, \dots, x_{m}), \dots, G_{n} (x_{1}, \dots, x_{m})) \end{array}

are absolute for $M$ .