Solution
Related Formula
2x = 2 x xCore Logic
Given equation: 2 ³ x + 2x x + 4 x - 4 = 0 Expand 2x:
2 ³ x + 2 x ² x + 4 x - 4 = 0Factor out 2 x from the first two terms:
2 x ( ² x + ² x) + 4 x - 4 = 0Since ² x + ² x = 1:
2 x (1) + 4 x - 4 = 0 6 x - 4 = 0 ⇒ x = (4)/(6) = (2)/(3)Step 1: Finding appropriate interval for exactly 3 roots
We need exactly 3 solutions in [0, (nπ)/(2)]. The line y = 2/3 intersects the sine wave y = x twice in every 2π interval. In [0, π], there are 2 solutions. In [π, 2π], there are 0 solutions. In [2π, 3π], there are 2 solutions (total 4 solutions). To get exactly 3 solutions, the interval must stretch past the first root in [2π, 3π], but not reach the second root in that interval. However, the interval is defined as (nπ)/(2). Let's check endpoints (nπ)/(2): For n=4: [0, 2π] has 2 solutions. For n=5: [0, (5π)/(2)] includes [2π, 2π + (π)/(2)]. Since x = 2/3 happens in (0, π/2), there is exactly 1 solution in [2π, 5π/2]. Thus, total solutions = 3 for n=5.
Step 2: Solving quadratic equation
Given n = 5, the quadratic equation is:
x² + 5x + 2 = 0Using quadratic formula:
x = -5 ± √(25 - 8)2 = -5 ± √(17)2The roots are approximately (-5 ± 4.12)/(2), which evaluates to roughly -0.44 and -4.56. Both roots are strictly negative.
Step 3: Determining interval membership
Since both roots are negative, they belong to the interval (-∞, 0).
Pattern Recognition
Collapsing complex trigonometric expressions often yields c₁ x = c₂. Overlaying horizontal line intersections on the sine graph bounds n rapidly by counting nodes.
Chapter Mix
Class 11 Maths: Trigonometric Functions Class 11 Maths: Complex Numbers and Quadratic Equations