Algebra
Vieta's checks
A two-line verification that catches most transcription errors without redoing the main calculation.
The Formula
Sum of roots = -b/a, product = c/a
A two-line verification that catches most transcription errors without redoing the main calculation.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| x1 + x2 | Sum of the two roots | — | Should equal -b/a exactly, apart from rounding. |
| x1 x x2 | Product of the two roots | — | Should equal c/a exactly, apart from rounding. |
What Each Symbol Means
x1 + x2
Sum of the two roots
Should equal -b/a exactly, apart from rounding.
x1 x x2
Product of the two roots
Should equal c/a exactly, apart from rounding.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to solve a quadratic equation page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Solve A Quadratic Equation, filed under Math. Every number the guide produces comes from substituting into this one line.