Pregunta
Use the given zero to find the remaining zeros of the function. \( f(x)=x^{3}-7 x^{2}+9 x-63 ; \) zero: \( -3 i \) The remaining zero(s) of \( f \) is(are) (Use a comma to separate answers as needed.)
Ask by Rogers Greene. in the United States
Feb 27,2025
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The remaining zero of \( f \) is \( 7 \).
Solución
To find the remaining zeros of the function \( f(x) = x^3 - 7x^2 + 9x - 63 \) given that one zero is \( -3i \), we can use the fact that the coefficients of the polynomial are real numbers. This means that the complex zeros must occur in conjugate pairs. Therefore, if \( -3i \) is a zero, then its conjugate \( 3i \) is also a zero.
Next, we can find the remaining zero by performing polynomial long division or synthetic division to divide \( f(x) \) by the quadratic polynomial formed by the two complex zeros, which is \( (x + 3i)(x - 3i) = x^2 + 9 \).
Let's perform the division of \( f(x) \) by \( x^2 + 9 \) to find the remaining zero.
1. **Divide \( f(x) \) by \( x^2 + 9 \)**:
- The first term of \( f(x) \) is \( x^3 \), and the first term of \( x^2 + 9 \) is \( x^2 \). We divide \( x^3 \) by \( x^2 \) to get \( x \).
- Multiply \( x \) by \( x^2 + 9 \) to get \( x^3 + 9x \).
- Subtract this from \( f(x) \):
\[
(x^3 - 7x^2 + 9x - 63) - (x^3 + 9x) = -7x^2 - 63
\]
- Now, divide \( -7x^2 \) by \( x^2 \) to get \( -7 \).
- Multiply \( -7 \) by \( x^2 + 9 \) to get \( -7x^2 - 63 \).
- Subtract this from the previous result:
\[
(-7x^2 - 63) - (-7x^2 - 63) = 0
\]
The result of the division is \( x - 7 \).
2. **Set the quotient equal to zero to find the remaining zero**:
\[
x - 7 = 0 \implies x = 7
\]
Thus, the remaining zeros of the function \( f(x) \) are \( 3i, -3i, 7 \).
The remaining zero(s) of \( f \) is(are) \( 7 \).
Respondido por UpStudy AI y revisado por un tutor profesional
Como
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Beyond the Answer
Since the function \( f(x) = x^{3} - 7x^{2} + 9x - 63 \) has a complex zero \( -3i \), its conjugate \( 3i \) must also be a zero. To find the remaining zero, we can use polynomial division or synthetic division to divide the cubic polynomial by the quadratic factor formed by the complex zeros, \( (x + 3i)(x - 3i) = x^2 + 9 \). Carrying out the division, we find \( f(x) \) can be expressed as \( (x^2 + 9)(x - 7) \). Thus, the third remaining zero is \( 7 \). The complete list of zeros is \( -3i, 3i, 7 \).
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