Question

Find all the zeros of the following functions using any method.
f(x)=x^3-x^2-34x-56
I already got the possible rational zeros which are
+or- 1, 2, 4, 7, 8, 14, 28, 56

Answer 1

Not being sure is such a bad thing :)
Why don't you see if any of those "possible" rational zeros is actually a zero? ^.^

Answer 2

i did i tried 2,4,7 they all gave me zero when i put them in for x, but i dont know what to do know. I have tried sythentic division and it doesn't give me the right outcome

Answer 3

You tried 2, did you?
How do you get zero?

Answer 4

oh i did -2 :P

Answer 5

And what about 4? How do you get zero?

Answer 6

same with -4

Answer 7

the only one that gave me a zero without having to add a - was 7

Answer 8

Okay so you already have three zeros...
Why are you so worried, then?

That should be all of them, silly XD
A cubic polynomial would have exactly three zeros...

Answer 9

wait thats all i need to do :O

Answer 10

Your question DOES say find all the zeros of the function using any method, it seems you used Rational Root theorem or something...

Anyway, you already have the three zeros, so what's left to fuss about? ^.^

Answer 11

Wow *facepalm* thank you so much haha

Answer 12

Oh, and just to sound all professional and what-not,why not throw in "since it's a monic polynomial" its factorisation should be
(x+2)(x+4)(x-7)

and put this question to rest XD

Answer 13

wait so its (x+2)(x+4)(x-7) and not (x-2)(x-4)(x+7)

Answer 14

No...

If a polynomial has a factor (x+r), then the zero is -r, not r.

Think of it this way...
If it were
x-2 = 0

Is the zero of the polynomial -2 or 2? ;)

Answer 15

ah ok thx again