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Cubic & Quartic Equation Calculator

Enter polynomial coefficients to estimate its real roots, multiplicities and residuals in your browser.

Example: x³ − 1 = 0 has the real root x = 1.

Real roots only; this does not calculate complex roots or symbolic factors. Coefficients are limited to ±1,000,000. Very small leading coefficients are rejected. Results are numerical estimates; residual is |P(root)|.

How do I use the polynomial root calculator?

Choose a cubic or quartic, enter coefficients from the highest power to the constant term, then calculate. Roots are numerical estimates and are listed in order.

Frequently asked questions

How do I use the polynomial root calculator?

Choose a cubic or quartic, enter coefficients from the highest power to the constant term, then calculate. Roots are numerical estimates and are listed in order.

Are my equation coefficients uploaded?

No. The calculation runs locally in this browser; your coefficients are not sent to a server.

Does this calculator show complex roots?

No. It estimates real roots only. It does not calculate complex roots, symbolic factors or a general computer-algebra solution.

Are the roots exact?

No. Roots are numerical estimates. The residual |P(root)| indicates how close the displayed estimate is to zero when substituted into the polynomial.