Shortcut Trick
If (x + a) and (x + b) are factors of a quadratic equation, then the equation is given by x2 + (a + b)x + ab = 0.
Comparing (x − 2) and (x + 3) with (x + a) and (x + b), we get a = −2 and b = 3.
The coefficient k1 = a + b = −2 + 3 = 1.
The constant term k2 = a × b = −2 × 3 = −6.
∴ The correct answer is k1 = 1, k2 = −6.
Alternate Method
Given: The factors of the quadratic equation x2 + k1x + k2 = 0 are (x − 2) and (x + 3).
Formula Used: If (x − r1) and (x − r2) are factors, then the polynomial P(x) = (x − r1)(x − r2).
⇒ P(x) = (x − 2)(x + 3)
⇒ P(x) = x(x + 3) − 2(x + 3)
⇒ P(x) = x2 + 3x − 2x − 6
⇒ P(x) = x2 + x − 6
⇒ Comparing this result with the given equation x2 + k1x + k2 = 0:
⇒ k1 = Coefficient of x = 1
⇒ k2 = Constant term = −6
This confirms that k1 = 1 and k2 = −6 is the correct solution.
∴ The correct answer is k1 = 1, k2 = −6.
Additional Information
Factor Theorem
If (x − a) is a factor of a polynomial f(x), then f(a) = 0. This can be used to set up simultaneous equations to find unknown coefficients.
Vieta's Formulas
For a quadratic equation ax2 + bx + c = 0 with roots α and β, the sum of roots is −b/a and the product of roots is c/a.
Quadratic Construction
A quadratic equation can be formed as x2 − (Sum of roots)x + (Product of roots) = 0 when the roots are known.