Mathematics
Find the value of k, if x - 1 is a factor of p(x) in each of the following cases:
(i) p(x) = x2 + x + k
(ii) p(x) = 2x2 + kx +
(iii) p(x) = kx2 - x + 1
(iv) p(x) = kx2 - 3x + k
Polynomials
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Answer
(i) p(x) = x2 + x + k
⇒ x - 1 = 0
⇒ x = 1
Putting x = 1 we get,
p(1) = (1)2 + 1 + k
= 1 + 1 + k
⇒ 2 + k = 0
⇒ k = -2
So the value of k = -2
(ii) p(x) = 2x2 + kx +
⇒ x - 1 = 0
⇒ x = 1
Putting x = 1 we get,
p(1) = 2(1)2 + k(1) +
⇒ 2 + k +
⇒ k = -2 -
⇒ k = -(2 + )
So the value of k = -(2 + )
(iii) p(x) = kx2 - x + 1
⇒ x - 1 = 0
⇒ x = 1
Putting x = 1 we get,
p(1) = k(1)2 - (1) + 1
⇒ k - + 1 = 0
⇒ k = - 1
So the value of k = - 1
(iv) p(x) = kx2 - 3x + k
⇒ x - 1 = 0
⇒ x = 1
Putting x = 1 we get,
p(1) = k(1)2 -3(1) + k
= k - 3 + k
⇒ 2k - 3 = 0
⇒ 2k = 3
⇒ k =
So the value of k =
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