Assume that (x-4) is a factor of 2x^2-4x-z. What is the value of z?
How would you set it up to use the foil method?
Assume that (x-4) is a factor of 2x^2-4x-z. What is the value of z?
How would you set it up to use the foil method?
Let:
$ \displaystyle f(x)=2x^2-4x-z$
Now, if $x-4$ is a factor of $f$, then we must have:
$ \displaystyle f(4)=0$
So, this allows us to write:
$ \displaystyle 2(4)^2-4(4)-z=0$
Can you proceed?