The number of integral solutions of equation 2|x|(x2 + 1) = 5x2 is?
Explanation:
Case 1: x ≥ 0 ⇒ |x| = x ∴ 2 × x × (x2 + 1) = 5x2 ⇒ 2x(x2 + 1) = 5x2 ⇒ 2x(x2 + 1) - 5x2 = 0 ⇒ x[2(x2 + 1) - 5x] = 0 ⇒ x(2x2 – 5x + 2) = 0 ⇒ x(2x2 – 4x - x + 2) = 0 ⇒ x[2x(x – 2) - (x - 2)] = 0 ⇒ x(2x - 1)(x - 2) = 0 ⇒ x = 0 or ½ or 2. We need only integral solutions hence acceptable answers are 0 and 2.
Case 2: x < 0 ⇒ |x| = -x ∴ 2 × -x × (x2 + 1) = 5x2 ⇒ -2x(x2 + 1) = 5x2 ⇒ 2x(x2 + 1) + 5x2 = 0 ⇒ x[2(x2 + 1) + 5x] = 0 ⇒ x(2x2 + 5x + 2) = 0 ⇒ x(2x2 + 4x + x + 2) = 0 ⇒ x[(2x(x + 2) + (x + 2)] = 0 ⇒ x(2x + 1)(x + 2) = 0 ⇒ x = 0 or -1/2 or -2 We need only integral solutions hence acceptable answers are 0 and -2.
∴ Acceptable integral solutions are -2, 0 and 2, i.e., 3 integral solutions.
Hence, 3.
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