SOLUTION: i need help with this question :Find a polynomial function of lowest degree with rational coefficients that has the given numbers as some of its zeros. radical 2,5i thank

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Question 1027286: i need help with this question :Find a polynomial function of lowest degree with rational coefficients that has the given numbers as some of its zeros.
radical 2,5i

thank you!

Answer by ikleyn(52794) About Me  (Show Source):
You can put this solution on YOUR website!
i need help with this question :Find a polynomial function of lowest degree with rational coefficients that has the given numbers as some of its zeros.
radical 2,5i

thank you!
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1. If the polynomial with rational coefficients has the root  sqrt%282%29,  it also has the root -sqrt%282%29.


2. If the polynomial with real coefficients has the root 5i, it also has the complex conjugated root  -5i.


3. So, your polynomial must have the roots sqrt%282%29,  -sqrt%282%29,  5i  and  -5i.


4. If so, it must be divisible by the product %28x-sqrt%282%29%29%2A%28x-%28-sqrt%282%29%29%29%2A%28x-5i%29%2A%28x-%28-5i%29%29 = %28x-sqrt%282%29%29%2A%28x%2Bsqrt%282%29%29%2A%28x-5i%29%2A%28x%2B5i%29%29 = %28x%5E2+-2%29%2A%28x%5E2+%2B+25%29 .


5. If you are looking for the polynomial of lowest degree with such properties,
   it is exactly THIS polynomial f(x) = %28x%5E2+-2%29%2A%28x%5E2+%2B+25%29.