SOLUTION: Find a cubic polynomial in standard form with real coefficients, having the zeros 2 and 6i. Let the leading coefficient be 1

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Find a cubic polynomial in standard form with real coefficients, having the zeros 2 and 6i. Let the leading coefficient be 1      Log On


   



Question 999717: Find a cubic polynomial in standard form with real coefficients, having the zeros 2 and 6i. Let the leading coefficient be 1
Found 3 solutions by Fombitz, ikleyn, Alan3354:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Real coefficients means complex roots come in complex conjugate pairs.
f%28x%29=%28x-2%29%28x%2B6i%29%28x-6i%29
f%28x%29=%28x-2%29%28x%5E2%2B36%29
f%28x%29=x%5E3%2B36x-2x%5E2-72
f%28x%29=x%5E2-2x%5E2%2B36x-72

Answer by ikleyn(52803) About Me  (Show Source):
You can put this solution on YOUR website!
.
Find a cubic polynomial in standard form with real coefficients, having the zeros 2 and 6i. Let the leading coefficient be 1
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(x-2)*(x-6i)*(x-(-6i)) = %28x-2%29%2A%28x%5E2+%2B+36%29.

1.  If a polynomial with real coefficients has a complex root,  it has the conjugate complex number as a root,  too.

2.  If a polynomial  f(x)  of a degree  n  with leading coefficient  1  has  n  roots  x%5B1%5D, x%5B2%5D, . . . , x%5Bn%5D  then the polynomial is the product

      f(x) = %28x-x%5B1%5D%29%2A%28x-x%5B2%5D%29%2A+ellipsis+%2A+%28x-x%5Bn%5D%29.


Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Find a cubic polynomial in standard form with real coefficients, having the zeros 2 and 6i. Let the leading coefficient be 1
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If 6i is a zero then -6i is too.
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--> (x-2)*(x-6i)*(x+6i)
= %28x-2%29%2A%28x%5E2+%2B+36%29
= x%5E3+-+2x%5E2+%2B+36x+-+72