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If the zeros of the polynomial f(x) = 2×3 – 15×2 + 37x – 30 are in A.P., find them.

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explain AP,

if the zeroes are in AP; find them when f(x) = 2×3 – 15×2 + 37x – 30

class 10th rd Sharma polynomials

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  1. Solution:

    Let the zeros of the given polynomial be α, β and γ. (3 zeros as it’s a cubic polynomial)

    And given, the zeros are in A.P.

    So, let’s consider the roots as

    α = a – d, β = a and γ = a +d

    Where a is the first term and d is a common difference.

    From given f(x), a= 2, b= -15, c= 37 and d= 30

    ⇒ Sum of roots = α + β + γ = (a – d) + a + (a + d) = 3a = (-b/a) = -(-15/2) = 15/2

    So, calculating for a, we get 3a = 15/2 ⇒ a = 5/2

    ⇒ Product of roots = (a – d) x (a) x (a + d) = a(a2 –d2) = -d/a = -(30)/2 = 15

    ⇒ a(a2 –d2) = 15

    Substituting the value of a, we get

    ⇒ (5/2)[(5/2)2 –d2] = 15

    ⇒ 5[(25/4) –d2] = 30

    ⇒ (25/4) – d2 = 6

    ⇒ 25 – 4d2 = 24

    ⇒ 1 = 4d2

    ∴ d = 1/2 or -1/2

    Taking d = 1/2 and a = 5/2

    We get,

    The zeros as 2, 5/2 and 3

    Taking d = -1/2 and a = 5/2

    We get,

    The zeros as 3, 5/2 and 2

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