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 * {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 ❤