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f(x)=x^4+2x^3+6x^2+18x-27
We want to write a polynomial function with integral coefficients so that f(x)=0 has the given zeros. -3, 1, -3i To do so, recall the Complex Conjugates Theorem.
Complex Conjugates Theorem |
If f(x) is a polynomial with real coefficients, then the complex roots of f(x)=0 occur in conjugate pairs. |
This theorem states that if a + bi is a complex root, then a- bi is also a zero. Additionally, recall that if a is a zero of f(x)=0, then (x-a) is a factor of f(x).
Root | Factor |
---|---|
-3 | x-(-3) |
1 | x-1 |
-3i | x-(-3i) |
3i | x-3i |
Polynomial | f(x)= [x-(-3)] (x-1) [x-(-3i)](x-3i) |
- (- a)=a
(a+b)(a-b)=a^2-b^2
(a b)^m=a^m b^m
Calculate power
i^2=- 1
- a(- b)=a* b
Distribute (x^2+9)
Commutative Property of Addition