Math Problem Statement

Suppose the quadratic equation x^2 + bx + c = 0 has the solutions -7 + 4i and -7 - 4i. What are b and c?

Solution

The quadratic equation given is:

x2+bx+c=0x^2 + bx + c = 0

It has solutions 7+4i-7 + 4i and 74i-7 - 4i. These solutions are complex conjugates, meaning the sum and product of the roots will help us determine the coefficients bb and cc.

Using Vieta's formulas:

For a quadratic equation x2+bx+c=0x^2 + bx + c = 0 with roots r1r_1 and r2r_2:

  1. The sum of the roots is b-b.
  2. The product of the roots is cc.

In this case:

  • The sum of the roots (7+4i)+(74i)=14(-7 + 4i) + (-7 - 4i) = -14. So, b=14-b = -14, which gives b=14b = 14.

  • The product of the roots (7+4i)(74i)=(7)2(4i)2=49(16)=49+16=65( -7 + 4i)( -7 - 4i) = (-7)^2 - (4i)^2 = 49 - (-16) = 49 + 16 = 65. So, c=65c = 65.

Therefore:

  • b=14b = 14
  • c=65c = 65

Would you like more details or clarifications?

Here are 5 related questions to explore this further:

  1. What happens if the roots are not complex conjugates?
  2. How do you derive the quadratic formula from Vieta's relations?
  3. Can you use another method to find bb and cc from the given roots?
  4. How are the coefficients related to the nature of the roots (real vs. complex)?
  5. Can Vieta’s formulas be used for higher-degree polynomials?

Tip: For quadratic equations with complex conjugate roots, the imaginary parts always cancel out in the sum of the roots, leaving only the real part to determine bb.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Complex Numbers

Formulas

Sum of the roots of a quadratic equation: -b = r1 + r2
Product of the roots of a quadratic equation: c = r1 * r2

Theorems

Vieta's Formulas

Suitable Grade Level

Grades 10-12