# Math Help - polynomial

1. ## polynomial

Hello
is this right?

Form a polynomial f(x) with real coheficients having the given degree and zeros.
zeros: -1,3i. degree 3
I got x^3+x^2-9x-9.

thank you so much

2. Originally Posted by girl1985
Hello
is this right?

Form a polynomial f(x) with real coheficients having the given degree and zeros.
zeros: -1,3i. degree 3
I got x^3+x^2-9x-9.

thank you so much
did you mean to type 3 instead of 3i? if not, you're wrong. the function you gave has the zeros -1, 3, -3

3. Thank you jhevon.

So what would be the answer?

4. Originally Posted by girl1985
Hello
is this right?

Form a polynomial f(x) with real coheficients having the given degree and zeros.
zeros: -1,3i. degree 3
I got x^3+x^2-9x-9.

thank you so much
Assuming it is a polynomial in R[x] (over the reals).

Then if 3i is a solution then so is -3i.

That means all the polynomials are:
K(x+1)(x-3i)(x+3i)
Where K is a non-zero constant polynomial.

Multiply those factors,
K(x^3+x^2+9x+9)

It seems thou are wrong.

5. Originally Posted by girl1985
Thank you jhevon.

So what would be the answer?
x^3 + x^2 + 9x + 9, you had a -9x and -9, they should have been +, do you see where you made your mistake?