Math Problem Statement

X^2+(k-4)x+1=0 where k has no real roots, find the set of possible values of k

Solution

To solve for the values of kk such that the quadratic equation x2+(k4)x+1=0x^2 + (k-4)x + 1 = 0 has no real roots, we need to analyze the discriminant of the quadratic equation.

For a general quadratic equation of the form ax2+bx+c=0ax^2 + bx + c = 0, the discriminant Δ\Delta is given by:

Δ=b24ac\Delta = b^2 - 4ac

In your equation, a=1a = 1, b=(k4)b = (k-4), and c=1c = 1. Therefore, the discriminant is:

Δ=(k4)24(1)(1)\Delta = (k-4)^2 - 4(1)(1)

Simplifying this expression:

Δ=(k4)24\Delta = (k-4)^2 - 4

For the quadratic equation to have no real roots, the discriminant must be less than zero:

(k4)24<0(k-4)^2 - 4 < 0

Now solve this inequality:

(k4)2<4(k-4)^2 < 4

Taking the square root of both sides:

k4<2|k-4| < 2

This implies:

2<k4<2-2 < k-4 < 2

Adding 4 to all parts of the inequality:

2<k<62 < k < 6

Thus, the set of possible values of kk such that the quadratic equation has no real roots is:

k(2,6)k \in (2, 6)

Would you like further details or have any questions?

Related questions:

  1. What happens if the discriminant is equal to zero?
  2. How would the roots change if k=2k = 2?
  3. What if k>6k > 6, how does the nature of the roots change?
  4. Can you give a similar quadratic equation where the roots are imaginary?
  5. How does completing the square help in finding the roots?

Tip: Always check the discriminant when analyzing the nature of the roots of quadratic equations!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Discriminant
Inequalities

Formulas

Quadratic equation: ax^2 + bx + c = 0
Discriminant: Δ = b^2 - 4ac
Inequality solving

Theorems

Discriminant of a quadratic equation

Suitable Grade Level

Grades 9-11