Mathematics

One factor of x3 - kx2 + 11x - 6 is x - 1. The value of k is :

  1. -6

  2. 12

  3. 6

  4. -12

Factorisation

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Answer

By factor theorem,

If x - a is a factor of polynomial f(x), then remainder f(a) = 0.

Given,

x - 1 is a factor of 8x2 - 7x + m.

⇒ x - 1 = 0

⇒ x = 1.

Substituting x = 1, in x3 - kx2 + 11x - 6 remainder will be zero.

⇒ 13 - k(1)2 + 11(1) - 6 = 0

⇒ 1 - k + 11 - 6 = 0

⇒ 6 - k = 0

⇒ k = 6.

Hence, Option 3 is the correct option.

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