Roots of the equation x2 + 2x - 6 = 0 are:
- AOption (a)
-2 ±
- BOption (b)
-1 ±
- COption (c)
-3 ±
- DOption (d)
-1 ±
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Correct answer
-1 ±
Why this answer is correct
Shortcut Trick
For a quadratic equation in the form x2 + bx + c = 0 (where a = 1), the roots can be directly found using the formula: −(b/2) ± √((b/2)2 − c).
In this equation, b = 2 and c = −6.
Substituting the values: −(2/2) ± √((2/2)2 − (−6))
⇒ −1 ± √(1 + 6) = −1 ± √7.
∴ The correct answer is −1 ± √7.
Alternate Method
Given: The quadratic equation is x2 + 2x − 6 = 0.
Formula Used: The standard quadratic formula to find the roots of ax2 + bx + c = 0 is: x = [−b ± √(b2 − 4ac)] / 2a.
⇒ Here, the coefficients are: a = 1, b = 2, and c = −6.
⇒ Calculate the Discriminant (D): D = b2 − 4ac = (2)2 − 4 × 1 × (−6).
⇒ D = 4 + 24 = 28.
⇒ Now, substitute D into the formula: x = (−2 ± √28) / (2 × 1).
⇒ Since √28 = √(4 × 7) = 2√7, the expression becomes: x = (−2 ± 2√7) / 2.
⇒ Dividing both terms by 2, we get: x = −1 ± √7.
∴ The correct answer is −1 ± √7.
Additional Information
Nature of Roots
The nature depends on the Discriminant (D = b2 − 4ac): if D > 0, roots are real and distinct; if D = 0, roots are real and equal; if D < 0, roots are imaginary.
Sum and Product of Roots
For the equation ax2 + bx + c = 0, the Sum of roots (α + β) = −b/a and the Product of roots (αβ) = c/a.
Completing the Square
Roots can also be found by transforming the equation into a perfect square: (x + b/2a)2 = (b2 − 4ac) / 4a2.

