Subject

    Quantitative Aptitude

    Topic

    Algebra

    In the following question, one or two equation(s) is/are given. You have to solve both the equations and find the relation between ‘x’ and ‘y’ and mark correct answer. I. x4– 18x2+ 81 = 0 II. y4– 25y2+ 144 = 0

    ক)
    x > y
    খ)
    x ≥ y
    গ)
    x < y
    ঘ)
    x ≤ y
    ঙ)
    x = y or the relation cannot be determined

    Explanation

    We will solve both the equations separately. Equation I: x 4 – 18x 2 + 81 = 0 let x 2 = a, then a 2 – 18a + 81 = 0 ⇒ a 2 – 2 × a × 9 + (9) 2 = 0 By using the formula: (a + b) 2 = a 2 + 2ab + b 2 (a – 9)2 = 0 a = 9, 9 So, x = ±3, ±3 Equation II. y 4 – 25y2 + 144 = 0 let y 2 = b ⇒ b 2 – 25b + 144 = 0 ⇒ b 2 – 16b – 9b + 144 = 0 ⇒ b(b – 16) – 9(b – 16) = 0 ⇒ (b – 9) (b – 16) = 0 ⇒ b = 9, 16 So, y = ±3, ±4 Comparing the values of x and y, we get, Few value of x are greater than y and few are smaller, same is true for y too. So, relation cannot be determined.

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