Question

$if \: x {}^{2} - x - 42 = (x + k)(x + 6) \: then \: k =$
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Answer 1

Answer:

$k=-7$

Step-by-step explanation:

$x {}^{2} - x - 42 = (x + k)(x + 6)$

$x^2-x-42=x^2+(k+6)x+6k$

$k+6=-1$, $6k=-42$

$k=-7$

Answer 2

Answer:

k = -7

Step-by-step explanation:

x² - x - 42 = (x + k) (x + 6)

x² - x - 42 = x² + 6x + kx + 6k

-x - 42 = 6x + kx + 6k

-x - 6x - 42 = kx + 6k

-7x - 42 = kx + 6k

-7 ( x + 6 ) = k ( x + 6 )

- 7 = k

{ k = - 7 }