Question

The value of k, for which the polynomial x3 + kx2+3x - 9 has 3 as its zero, is
(a) 9
(b) - 3
(c) 12
(d) - 9​

Answer 1

$Let \: the \: polynomial \: p(x) = x^{3}+kx^{2}+3x-9$

$Given \: 3 \: is \: a \: zero \: of \: p(x)$

$p(3) = 0$

$\implies 3^{3} + k \times 3^{2} + 3\times 3 - 9 = 0$

$\implies 27 + 9k + 9 - 9 = 0$

$\implies 9k + 27 = 0$

$\implies 9k = -27$

$\implies k = \frac{-27}{9}$

$\implies k = - 3$

Therefore.,

$\red { Value \:of \: k } \green { = -3 }$

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Answer 2

Answer:

the answer is thea of question is -9