Question

Find the value of k, if p(x)= x³ + kx²-4x+5 for p(3)=0.

Answer 1

27+9k-12+5=0

20+9k=0

k=-20/9

Answer 2

The value of k is $\frac{-20}{9}$

Solution:

Given that,

$p(x) = x^3 + kx^2 -4x + 5$

We have to find value of "k"

Given, p(3) = 0

Substitute x = 3 in given,

$p(3) = (3)^3 + k(3)^2 - 4(3) + 5\\\\(3)^3 + k(3)^2 - 4(3) + 5 = 0\\\\27 + 9k - 12 +5 =0\\\\9k +20 = 0\\\\9k = -20\\\\k = \frac{-20}{9}$

Thus value of k is $\frac{-20}{9}$

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