# Find a polynomial function that has the given zeros

• May 1st 2013, 01:07 PM
captaincrunch383
Find a polynomial function that has the given zeros
Please don't ignore this, I really need help. Sorry for making 2 threads in one day, I solved the other problem. This will be the last thread I make on here for a while, possibly months since next week is my last week of uni.

Find a polynomial function with real coefficients that has the given zeros:

5, -4+2i, -4-2i

• May 1st 2013, 01:13 PM
topsquark
Re: Find a polynomial function that has the given zeros
Quote:

Originally Posted by captaincrunch383
Please don't ignore this, I really need help. Sorry for making 2 threads in one day, I solved the other problem. This will be the last thread I make on here for a while, possibly months since next week is my last week of uni.

Find a polynomial function with real coefficients that has the given zeros:

5, -4+2i, -4-2i

First, why would we ignore it? Second you can post as many problems as you like, as long as you are working on them.

If a polynomial has complex zeros then they must come in complex conjugate pairs. Your complex zeros are complex conjugates so that works out.

You know three zeros. So your polynomial will be of the form: $(x - r_1 )(x - r_2 )(x - r_3 )$ where the r's are the zeros of the polynomial.

See what you are able to do with that.

-Dan
• May 1st 2013, 04:42 PM
captaincrunch383
Re: Find a polynomial function that has the given zeros
Quote:

Originally Posted by topsquark
First, why would we ignore it? Second you can post as many problems as you like, as long as you are working on them.

If a polynomial has complex zeros then they must come in complex conjugate pairs. Your complex zeros are complex conjugates so that works out.

You know three zeros. So your polynomial will be of the form: $(x - r_1 )(x - r_2 )(x - r_3 )$ where the r's are the zeros of the polynomial.

See what you are able to do with that.

-Dan

Thank you Dan. I'm afraid I still am a little lost, even with the information that you gave me.
• May 1st 2013, 04:55 PM
Plato
Re: Find a polynomial function that has the given zeros
Quote:

Originally Posted by captaincrunch383
Thank you Dan. I'm afraid I still am a little lost, even with the information that you gave me.

It is hard to think that you are asked to do this, but yet you can not do simple algebra!

Multiply this out: $[x-5]\cdot[x-(-4+2i)]\cdot[x-(-4-2i)]~.$
• May 1st 2013, 06:22 PM
captaincrunch383
Re: Find a polynomial function that has the given zeros
Quote:

Originally Posted by Plato
It is hard to think that you are asked to do this, but yet you can not do simple algebra!

Multiply this out: $[x-5]\cdot[x-(-4+2i)]\cdot[x-(-4-2i)]~.$

apparently i can't do simple algebra mr pluto. how am i supposed to multiply that out? [x-5] * [x+4+2i] * [x+4+2i] --- is that how it looks once the x is factored in? and i dont know how to multiply when it has 3 terms, i know how to do foil though.

make fun of me all you want sir, but i just want to get this over with.
• May 1st 2013, 06:42 PM
Plato
Re: Find a polynomial function that has the given zeros
Quote:

Originally Posted by captaincrunch383
apparently i can't do simple algebra mr pluto. how am i supposed to multiply that out? [x-5] * [x+4+2i] * [x+4+2i] --- is that how it looks once the x is factored in? and i dont know how to multiply when it has 3 terms, i know how to do foil though. make fun of me all you want sir, but i just want to get this over with.

I assure that I have no reason or desire to make fun of you,

But the simple fact is, if one does not know simply basic algebra then it is hopeless to try to help you.

Go back and do middle school algebra.
• May 1st 2013, 07:06 PM
captaincrunch383
Re: Find a polynomial function that has the given zeros
Quote:

Originally Posted by Plato
I assure that I have no reason or desire to make fun of you,

But the simple fact is, if one does not know simply basic algebra then it is hopeless to try to help you.

Go back and do middle school algebra.

why can't you just give me the answer? i don't know why you make it so difficult man..
• May 1st 2013, 09:37 PM
Prove It
Re: Find a polynomial function that has the given zeros
Quote:

Originally Posted by captaincrunch383
why can't you just give me the answer? i don't know why you make it so difficult man..

You seem to have us confused with a homework service. You are expected to complete your own work yourself, we can only give you some guidance in places where you are stuck.