Transform, then verify
Equivalent forms should agree. Use discriminants, roots, factoring, vertex form, substitution, matrix checks, or the Remainder Theorem where appropriate to verify the result rather than relying on a single opaque output.
Stable quadratic roots plus Vieta verification
The shared solver avoids catastrophic cancellation for widely separated real roots and checks roots against both P(x) and Vieta relationships.
Scope and precision
These are bounded browser calculators, not a universal computer algebra system. WebToolArc keeps exact algebraic identities visible where practical, uses stable floating-point algorithms for numeric work, distinguishes undefined/no-solution/infinite-solution cases, and shows an independent check after the main Calculate action.