SOLUTION: Write a polynomial function of minimum degree with real coefficients whose zeros include those listed. Write the polynomial in standard form. 7, -11, and 2 + 8i

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Write a polynomial function of minimum degree with real coefficients whose zeros include those listed. Write the polynomial in standard form. 7, -11, and 2 + 8i      Log On


   



Question 1100942: Write a polynomial function of minimum degree with real coefficients whose zeros include those listed. Write the polynomial in standard form.
7, -11, and 2 + 8i

Found 2 solutions by stanbon, KMST:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Write a polynomial function of minimum degree with real coefficients whose zeros include those listed. Write the polynomial in standard form.
7, -11, and 2 + 8i
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2-8i is also a zero
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f(x) = (x-7)(x+11)((x-2)-8i)((x-2)+8i)
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f(x) = (x-7)(x+11)((x-2)^2+64)
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f(x) = (x-7)(x+11)(x^2-2x+68)
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Cheers,
Stan H.
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Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
If complex number 2+%2B+8i is a zero of a polynomial with real coefficients,
so is the conjugate complex number, 2+-+8i .
So, we know four zeros of the function,
and for each zero , there must be a factor of the form x-zero .
As a consequence, the simplest polynomial function of minimum degree,
with real coefficients, and including those four zeros is
f%28x%29=%28x-7%29%28x-%28-11%29%29%28x-%282+%2B+8i%29%29%28x-%282+-+8i%29%29 .
Now, we just have to simplify and multiply.
f%28x%29=%28x-7%29%28x%2B11%29%28x-2-+8i%29%28x-2%2B+8i%29
f%28x%29=%28x-7%29%28x%2B11%29%28%28x-2%29-+8i%29%28%28x-2%29%2B+8i%29
f%28x%29=%28x-7%29%28x%2B11%29%28%28x-2%29%5E2-+%288i%29%5E2%29
f%28x%29=%28x-7%29%28x%2B11%29%28x%5E2-4x%2B4-8%5E2%28i%29%5E2%29
f%28x%29=%28x-7%29%28x%2B11%29%28x%5E2-4x%2B4-64%28-1%29%29
f%28x%29=%28x-7%29%28x%2B11%29%28x%5E2-4x%2B4%2B64%29
f%28x%29=%28x%5E2%2B4x-77%29%28x%5E2-4x%2B68%29
f%28x%29=x%5E4-25x%5E2%2B580x-5230