Question

Given f(x)=2x^3+kx-9 and x-1is a factor of f(x), then what is the value of k?

Answer 1

When it says the "x - 1 " is the factor of that function means when you find the root of the phrase x - 1 which is x = 1 , put it in the function then you have to get zero for the answer :

thus :

$f(1) = 0$

Thus :

$2 \times {1}^{3} + k(1) - 9 = 0$

So :

$2 + k - 9 = 0$

$k - 7 = 0$

Add both sides 7

$k - 7 + 7 = 0 + 7$

$k = 7$

There you go...

Have a great day ❤