import { type Rule } from "../rule.js";
export type FactorOutNegativeParams = Record<string, never>;
/**
 * Factor −1 out of a sum — negate every term and hang a Neg outside:
 *   1 − 2x  ~>  −(−1 + 2x)        x + 3  ~>  −(−x − 3)
 * An exact identity (double negation), so it emits nothing. The crucial move
 * for factoring by grouping when the leading coefficient ≠ 1: it flips a
 * group's binomial to match its neighbour's sign, e.g. (1−2x) into a form
 * structurally equal to (2x−1), so the shared factor can be pulled out.
 * Each term's body survives by identity (neg() reuses the term, or unwraps a
 * Neg); only the Neg wrappers change. The inner sum keeps the original id.
 */
export declare const factorOutNegative: Rule<FactorOutNegativeParams>;
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