Related Formula
Difference of roots formula:
(α - β)² = (α + β)² - 4αβ$$(\alpha - \beta)^2 = (\alpha + \beta)^2 - 4\alpha\beta$$
For 12x² - 20x + 3λ = 0$12x^2 - 20x + 3\lambda = 0$: α + β = (20)/(12) = (5)/(3)$\alpha + \beta = \frac{20}{12} = \frac{5}{3}$, αβ = (3λ)/(12) = (λ)/(4)$\alpha\beta = \frac{3\lambda}{12} = \frac{\lambda}{4}$.
Core Logic
Square the inequality (1)/(2) ≤ |α - β| ≤ (3)/(2)$\frac{1}{2} \le |\alpha - \beta| \le \frac{3}{2}$:
(1)/(4) ≤ (α - β)² ≤ (9)/(4)$$\frac{1}{4} \le (\alpha - \beta)^2 \le \frac{9}{4}$$
(1)/(4) ≤ (25)/(9) - λ ≤ (9)/(4)$$\frac{1}{4} \le \frac{25}{9} - \lambda \le \frac{9}{4}$$
-(91)/(36) ≤ -λ ≤ -(19)/(36) (19)/(36) ≤ λ ≤ (91)/(36)$$-\frac{91}{36} \le -\lambda \le -\frac{19}{36} \implies \frac{19}{36} \le \lambda \le \frac{91}{36}$$
Step 1: Integer Values of Lambda
Since λ in Z$\lambda \in \mathbb{Z}$, the valid integer values are λ = 1, 2$\lambda = 1, 2$.
Sum = 1 + 2 = 3$$\text{Sum} = 1 + 2 = 3$$
Pattern Recognition
Convert root difference inequality into quadratic discriminant bounds for quick integer extraction.
Chapter Mix
Class 11 Maths: Quadratic Equations