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f(x)=x^4-3x^3-9x^2+77x+150
We want to write a polynomial function with integral coefficients so that f(x)=0 has the given zeros. -2, -3, 4-3i To do so, recall the Complex Conjugates Theorem.
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Complex Conjugates Theorem |
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If f(x) is a polynomial with real coefficients, then the complex roots of f(x)=0 occur in conjugate pairs. |
| Root | Factor |
|---|---|
| -2 | x-(-2) |
| -3 | x-(-3) |
| 4-3i | x-(4-3i) |
| 4+3i | x-(4+3i) |
| Polynomial | f(x)= [x-(-2)] [x-(-3)] [x-(4-3i)][x-(4+3i)] |
Let's simplify the polynomial by applying the Distributive Property. For simplicity, we will start by multiplying the first two factors and the last two factors separately. [x-(-2)] & * [x-(-3)] [x-(4-3i)] & * [x-(4+3i)] After we find these products, we will multiply the obtained expressions.
Let's continue by finding the product of the last two factors.
Distribute -1
Add parentheses
(a+b)(a-b)=a^2-b^2
(a-b)^2=a^2-2ab+b^2
(a b)^m=a^m b^m
Calculate power
i^2=- 1
- a(- b)=a* b
Add terms
Finding the product of these two polynomials will give us the desired polynomial function.
Distribute (x^2-8x+25)
Distribute x^2
Distribute 5x
Distribute 6
Add and subtract terms