Question

Help please!
If (x + k) is a factor of f(x), which of the following must be true?
f(k) = 0
f(–k) = 0
A root of f(x) is x = k.
A y intercept of f(x) is x = –k.

Answer 1

If (x + k) is a factor of f(x), then f(x) = (x+k).g(x)

i think you can work it out from there

Answer 2

C??? because if f(x)=x+k) then wouldnt a root of f(x) x=k

Answer 3

f(-k)=0

Answer 4

almost
by definition of factor
f(x)= (x+k)* g(x)
what do we get when x= -k ?
putting in -k for x we get
f(-k) = (-k+k) * g(-k)

we don't know what g(-k) is, but we do know what (-k+k) is
what do we get for f(-k) ?

Answer 5

the answer is A

Answer 6

do you see
f(-k) = (-k+k) * g(-k) becomes
f(-k) = 0 * g(-k)
and 0 * anything is 0