Math Problem Statement

For what value(s) of "m" does the following quadratic have no real roots? 0=(3m+4)x^2+mx-0.5?

Solution

To determine the value(s) of mm for which the quadratic equation 0=(3m+4)x2+mx0.50 = (3m + 4)x^2 + mx - 0.5 has no real roots, we need to look at 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 If Δ<0\Delta < 0, the quadratic equation has no real roots.

Step 1: Identify aa, bb, and cc

From the equation: 0=(3m+4)x2+mx0.50 = (3m + 4)x^2 + mx - 0.5 we have:

  • a=3m+4a = 3m + 4
  • b=mb = m
  • c=0.5c = -0.5

Step 2: Set up the Discriminant Condition

To ensure there are no real roots, we need Δ<0\Delta < 0. Substituting aa, bb, and cc into the discriminant: Δ=b24ac=m24(3m+4)(0.5)\Delta = b^2 - 4ac = m^2 - 4(3m + 4)(-0.5) Simplify this expression: Δ=m2+2(3m+4)\Delta = m^2 + 2(3m + 4) Δ=m2+6m+8\Delta = m^2 + 6m + 8

Step 3: Set the Inequality

We want: m2+6m+8<0m^2 + 6m + 8 < 0 This is a quadratic inequality. We’ll first solve the corresponding equation: m2+6m+8=0m^2 + 6m + 8 = 0 Using the quadratic formula: m=6±6241821m = \frac{-6 \pm \sqrt{6^2 - 4 \cdot 1 \cdot 8}}{2 \cdot 1} m=6±36322m = \frac{-6 \pm \sqrt{36 - 32}}{2} m=6±42m = \frac{-6 \pm \sqrt{4}}{2} m=6±22m = \frac{-6 \pm 2}{2} So, m=2andm=4m = -2 \quad \text{and} \quad m = -4

Step 4: Test the Interval for mm

The inequality m2+6m+8<0m^2 + 6m + 8 < 0 is satisfied for values of mm between the roots. Therefore: 4<m<2-4 < m < -2

Conclusion

The quadratic equation has no real roots for values of mm in the interval: 4<m<2-4 < m < -2

Would you like further details on this solution, or do you have any other questions?


Here are some additional related questions you might explore:

  1. How does the discriminant help determine the nature of the roots?
  2. Can you find values of mm that would yield exactly one real root?
  3. How would the answer change if the constant term were different?
  4. What values of mm make the equation factorable?
  5. How does the solution change if mm is constrained to integer values?

Tip: When solving inequalities involving a quadratic, factor the expression and analyze the intervals between roots to find where the inequality holds.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Discriminant

Formulas

Discriminant formula: Δ = b^2 - 4ac
Quadratic formula: m = (-b ± √(b² - 4ac)) / 2a

Theorems

Discriminant Theorem

Suitable Grade Level

Grades 9-11