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Business Mathematics and Basic Statistics · Ch 1 — Quadratic Equations

Sridharacharya's Method (Statement)

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Sridharacharya's Method (Statement)

Sridharacharya's rule gives the roots of ax2+bx+c=0ax^2+bx+c=0 (a≠0a \neq 0) directly, as a formula, without repeating the completing-the-square steps each time:

x=−b±b2−4ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

This chapter uses the formula by statement only — the syllabus explicitly does not require its derivation or proof; §4's perfect-square method is the derivation route for a student who wants to see where it comes from, but examinations at this level expect direct application of the boxed formula above.

How to apply it:

  1. Write the equation in general form ax2+bx+c=0ax^2+bx+c=0 and read off aa, bb, cc (with their correct signs).
  2. Substitute into the formula and compute b2−4acb^2 - 4ac first (this quantity is called the discriminant, studied in detail in §6).
  3. Take the square root of the discriminant, then apply both the ++ and −- signs to get the two roots x1x_1 and x2x_2 (which coincide into one repeated root when the discriminant is exactly zero).
Note

Sridharacharya, the Mathematician …

Definition 4Sridharacharya's formula

x=−b±b2−4ac2ax = \dfrac{-b \pm \sqrt{b^2-4ac}}{2a} — gives both roots of ax2+bx+c=0ax^2+bx+c=0 directly from aa, bb, cc. Used here by statement …