Math Problem Statement

The equation (3k - 4)x - 2k^2x^2 - 2 = 0 has no real roots. Find the possible range of values of k.

Solution

The given equation is:

(3k4)x2k2x22=0(3k - 4)x - 2k^2x^2 - 2 = 0

It is stated that the equation has no real roots, and we are required to find the range of values for kk that satisfy this condition.

Step-by-Step Solution:

We can rewrite the given equation as a standard quadratic equation in terms of xx:

2k2x2+(3k4)x2=0-2k^2x^2 + (3k - 4)x - 2 = 0

This is of the form ax2+bx+c=0ax^2 + bx + c = 0, where:

  • a=2k2a = -2k^2
  • b=3k4b = 3k - 4
  • c=2c = -2

For a quadratic equation to have no real roots, its discriminant must be less than zero. The discriminant Δ\Delta for a quadratic equation ax2+bx+c=0ax^2 + bx + c = 0 is given by:

Δ=b24ac\Delta = b^2 - 4ac

Substitute the values of aa, bb, and cc:

Δ=(3k4)24(2k2)(2)\Delta = (3k - 4)^2 - 4(-2k^2)(-2)

Simplify the expression:

Δ=(3k4)216k2\Delta = (3k - 4)^2 - 16k^2

Now expand both terms:

Δ=(9k224k+16)16k2\Delta = (9k^2 - 24k + 16) - 16k^2

Δ=9k224k+1616k2\Delta = 9k^2 - 24k + 16 - 16k^2

Δ=7k224k+16\Delta = -7k^2 - 24k + 16

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

7k224k+16<0-7k^2 - 24k + 16 < 0

Solving the inequality:

We now solve the inequality 7k224k+16<0-7k^2 - 24k + 16 < 0 by finding its critical points (roots). We do this by solving the equality 7k224k+16=0-7k^2 - 24k + 16 = 0.

Use the quadratic formula:

k=(24)±(24)24(7)(16)2(7)k = \frac{-(-24) \pm \sqrt{(-24)^2 - 4(-7)(16)}}{2(-7)}

Simplify:

k=24±576+44814k = \frac{24 \pm \sqrt{576 + 448}}{-14}

k=24±102414k = \frac{24 \pm \sqrt{1024}}{-14}

k=24±3214k = \frac{24 \pm 32}{-14}

So, the two roots are:

k=24+3214=5614=4k = \frac{24 + 32}{-14} = \frac{56}{-14} = -4 and k=243214=814=47k = \frac{24 - 32}{-14} = \frac{-8}{-14} = \frac{4}{7}

Thus, the critical points are k=4k = -4 and k=47k = \frac{4}{7}.

Testing the intervals:

Since the quadratic 7k224k+16-7k^2 - 24k + 16 opens downwards (the coefficient of k2k^2 is negative), the inequality will be satisfied between the roots. Therefore, the solution to the inequality is:

47<k<4-\frac{4}{7} < k < 4

This is the range of values of kk such that the given quadratic equation has no real roots.

Final Answer:

47<k<4-\frac{4}{7} < k < 4

Would you like further details or have any questions? Here are five related questions for deeper understanding:

  1. How would the solution change if the discriminant were greater than zero?
  2. What does it mean for a quadratic equation to have complex roots?
  3. Could you derive the discriminant condition from first principles?
  4. How would you graph the quadratic expression in kk?
  5. What happens to the quadratic if k=4k = -4 or k=47k = \frac{4}{7}?

Tip: Always check the sign of the leading coefficient when determining the direction of a parabola (whether it opens upwards or downwards).

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Discriminant Analysis

Formulas

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

Theorems

Discriminant analysis for determining the nature of roots

Suitable Grade Level

Grades 9-12