Math Problem Statement

Solve this

Solve the quadratic equation x^2 + kx + 6 = 0 for different types of roots.

Solution

The question in the image asks to find the value of kk such that the quadratic equation x2+kx+6=0x^2 + kx + 6 = 0 has:

a) Two distinct roots
b) Double roots
c) No real roots

To solve this, we need to examine the discriminant Δ\Delta of the quadratic equation. The discriminant formula is given by:

Δ=b24ac\Delta = b^2 - 4ac

For the equation ax2+bx+c=0ax^2 + bx + c = 0, here a=1a = 1, b=kb = k, and c=6c = 6. So, the discriminant becomes:

Δ=k24(1)(6)=k224\Delta = k^2 - 4(1)(6) = k^2 - 24

Now, let's analyze the different cases based on the discriminant:

  1. Two distinct roots (real and different): This occurs when Δ>0\Delta > 0, meaning: k224>0k^2 - 24 > 0 k2>24k^2 > 24 Thus, k>24k > \sqrt{24} or k<24k < -\sqrt{24}.
    This gives the values of kk as: k>26ork<26k > 2\sqrt{6} \quad \text{or} \quad k < -2\sqrt{6}

  2. Double roots (a repeated real root): This occurs when Δ=0\Delta = 0, meaning: k224=0k^2 - 24 = 0 k2=24k^2 = 24 Thus, k=±24k = \pm \sqrt{24}.

  3. No real roots: This occurs when Δ<0\Delta < 0, meaning: k224<0k^2 - 24 < 0 k2<24k^2 < 24 Thus, 24<k<24-\sqrt{24} < k < \sqrt{24}.

Summary of conditions:

  • For two distinct roots: k>26k > 2\sqrt{6} or k<26k < -2\sqrt{6}.
  • For double roots: k=±24k = \pm \sqrt{24}.
  • For no real roots: 24<k<24-\sqrt{24} < k < \sqrt{24}.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Discriminant

Formulas

Discriminant formula: Δ = b^2 - 4ac

Theorems

Discriminant analysis for quadratic equations

Suitable Grade Level

Grades 9-12