Math Problem Statement

Solve f(x) = x^4 - 3x^3 - 5x^2 + 9x - 2 = 0, one root being 2 + √3.

Solution

The equation provided is:

f(x)=x43x35x2+9x2=0f(x) = x^4 - 3x^3 - 5x^2 + 9x - 2 = 0 with one root given as 2+32 + \sqrt{3}.

Since 2+32 + \sqrt{3} is a root, its conjugate 232 - \sqrt{3} will also be a root because the coefficients of the polynomial are real. This suggests that (x(2+3))(x(23))(x - (2 + \sqrt{3}))(x - (2 - \sqrt{3})) is a factor of the polynomial.

Let's first expand the product of these factors:

(x(2+3))(x(23))=(x23)(x2+3)(x - (2 + \sqrt{3}))(x - (2 - \sqrt{3})) = (x - 2 - \sqrt{3})(x - 2 + \sqrt{3}) This is a difference of squares:

(x2)2(3)2=(x2)23=x24x+1(x - 2)^2 - (\sqrt{3})^2 = (x - 2)^2 - 3 = x^2 - 4x + 1

Now, we know that x24x+1x^2 - 4x + 1 is a factor of the polynomial f(x)f(x). To find the remaining factors, we will divide f(x)f(x) by x24x+1x^2 - 4x + 1.

I'll perform the division now.The polynomial division yields:

f(x)=(x24x+1)(x2+x2)f(x) = (x^2 - 4x + 1)(x^2 + x - 2)

Since the remainder is 0, we know that f(x)f(x) factors completely as:

f(x)=(x24x+1)(x2+x2)f(x) = (x^2 - 4x + 1)(x^2 + x - 2)

Now, we solve the quadratic equation x2+x2=0x^2 + x - 2 = 0 to find the other roots. Factoring this quadratic:

x2+x2=(x1)(x+2)x^2 + x - 2 = (x - 1)(x + 2)

Thus, the complete factorization of f(x)f(x) is:

f(x)=(x(2+3))(x(23))(x1)(x+2)f(x) = (x - (2 + \sqrt{3}))(x - (2 - \sqrt{3}))(x - 1)(x + 2)

The roots of the equation are:

x=2+3,x=23,x=1,x=2x = 2 + \sqrt{3}, \quad x = 2 - \sqrt{3}, \quad x = 1, \quad x = -2

Would you like more details or have any questions?

Related Questions:

  1. How do you find roots of higher-degree polynomials?
  2. What is the difference between rational and irrational roots?
  3. How does the conjugate root theorem apply to polynomials with real coefficients?
  4. How can polynomial division help in factorization?
  5. What is the significance of the factor theorem in solving polynomials?

Tip:

Always check if the given polynomial has complex roots by applying the discriminant for quadratics when simplifying.

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Math Problem Analysis

Mathematical Concepts

Polynomial Equations
Quadratic Factorization
Irrational Roots
Conjugate Root Theorem

Formulas

(x - (a + b))(x - (a - b)) = (x - a)^2 - b^2
Polynomial division
Factorization of quadratic equations

Theorems

Conjugate Root Theorem
Factor Theorem

Suitable Grade Level

Grades 10-12