Question

if 5 is a zero of x³+kx²+4x+5 find k​

Answer 1

Answer:

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Step-by-step explanation:

Putting x = 5

$x {}^{3} +kx {}^{2} +4x+5 = 0\\ \\ (5) {}^{3} + k(5) {}^{2} + 4(5) + 5 = 0 \\ \\ 125 + 25k + 20 + 5 = 0 \\ \\ 150 + 25k = 0 \\ \\ 25k = - 150 \\ \\ k = \frac{ - 150}{25} \\ \\ k = - 6$

Answer 2

Answer:

- 6

Step-by-step explanation:

x = 5

Let p ( x ) = x³ + kx² + 4x + 5.

p ( 5 ) = 0

( 5 )³ + k ( 5 )² + 4 ( 5 ) + 5 = 0

125 + 25k + 20 + 5 = 0

25k + 125 + 20 + 5 = 0

25k + 150 = 0

25k = - 150

k = - 150 / 25

k = - 6