Math Problem Statement

solve

Write a polynomial function f of least degree that has rational coefficients, a leading coefficient of 1, and the given zeros 0, 2 - √2, 2 + 3i.

Solution

To solve this problem, we need to construct a polynomial with the following properties:

  1. It has rational coefficients.
  2. The leading coefficient is 1.
  3. It has the given zeros 00, 222 - \sqrt{2}, 2+3i2 + 3i.

Step 1: Rational Coefficients

Since the polynomial must have rational coefficients:

  • If 222 - \sqrt{2} is a zero, its conjugate 2+22 + \sqrt{2} must also be a zero.
  • If 2+3i2 + 3i is a zero, its conjugate 23i2 - 3i must also be a zero.

Thus, the zeros of the polynomial are: 0,22,2+2,2+3i,23i.0, 2 - \sqrt{2}, 2 + \sqrt{2}, 2 + 3i, 2 - 3i.

Step 2: Form the Polynomial

The polynomial can be constructed by multiplying the factors corresponding to these roots: f(x)=x(x(22))(x(2+2))(x(2+3i))(x(23i)).f(x) = x \cdot \big(x - (2 - \sqrt{2})\big) \cdot \big(x - (2 + \sqrt{2})\big) \cdot \big(x - (2 + 3i)\big) \cdot \big(x - (2 - 3i)\big).

Step 3: Simplify the Factors

Real Roots:

The factors for 222 - \sqrt{2} and 2+22 + \sqrt{2} combine into: (x(22))(x(2+2))=(x2+2)(x22).\big(x - (2 - \sqrt{2})\big)\big(x - (2 + \sqrt{2})\big) = \big(x - 2 + \sqrt{2}\big)\big(x - 2 - \sqrt{2}\big). Using the difference of squares: =(x2)2(2)2=(x2)22.= (x - 2)^2 - (\sqrt{2})^2 = (x - 2)^2 - 2.

Complex Roots:

The factors for 2+3i2 + 3i and 23i2 - 3i combine into: (x(2+3i))(x(23i))=(x23i)(x2+3i).\big(x - (2 + 3i)\big)\big(x - (2 - 3i)\big) = \big(x - 2 - 3i\big)\big(x - 2 + 3i\big). Using the difference of squares: =(x2)2(3i)2=(x2)2(9)=(x2)2+9.= (x - 2)^2 - (3i)^2 = (x - 2)^2 - (-9) = (x - 2)^2 + 9.

Combine All Factors:

Now include xx: f(x)=x((x2)22)((x2)2+9).f(x) = x \cdot \big((x - 2)^2 - 2\big) \cdot \big((x - 2)^2 + 9\big).

Step 4: Expand the Polynomial

Let y=(x2)2y = (x - 2)^2. Then: f(x)=x(y2)(y+9).f(x) = x \cdot (y - 2) \cdot (y + 9). First expand (y2)(y+9)(y - 2)(y + 9): (y2)(y+9)=y2+9y2y18=y2+7y18.(y - 2)(y + 9) = y^2 + 9y - 2y - 18 = y^2 + 7y - 18. Substitute back y=(x2)2y = (x - 2)^2: f(x)=x((x2)4+7(x2)218).f(x) = x \cdot \big((x - 2)^4 + 7(x - 2)^2 - 18\big).

Expand (x2)2=x24x+4(x - 2)^2 = x^2 - 4x + 4, then substitute and simplify further if needed.

Would you like me to continue with full expansion or clarify anything? Let me know!

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Math Problem Analysis

Mathematical Concepts

Polynomial Functions
Complex Numbers
Conjugate Zeros Theorem
Factoring

Formulas

Difference of squares: (a - b)(a + b) = a^2 - b^2
Quadratic expressions: ax^2 + bx + c

Theorems

Conjugate Zeros Theorem
Fundamental Theorem of Algebra

Suitable Grade Level

Grades 10-12