Identify the type of conic section and convert Ax²+Cy²+Dx+Ey+F=0 to standard form by completing the square.
| Condition | Conic Type | Discriminant B²−4AC |
|---|---|---|
| A = C ≠ 0 | Circle | < 0 |
| A ≠ C, same sign | Ellipse | < 0 |
| A and C opposite signs | Hyperbola | > 0 |
| A = 0 or C = 0 (not both) | Parabola | = 0 |
| A = 0 and C = 0 | Line / Degenerate | — |
Ax² + Dx = A(x + D/2A)² − D²/4A
General idea: Group terms by variable, factor out leading coefficients, then add the square of the half-coefficient to both sides.
For x: Ax² + Dx = A[x² + (D/A)x] = A[(x + D/2A)² − (D/2A)²]
For y: Cy² + Ey = C[y² + (E/C)y] = C[(y + E/2C)² − (E/2C)²]
After completing both squares, move constants to the right side and divide to put 1 (or the conic form) on the right.
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