Math Problem Statement

Determine an equation of the form ax^2 + bx + c = 0 if the roots are -3/4 and 5. Options: A) 4x^2 - 17x - 15 = 0, B) 4x^2 + 17x - 15 = 0, C) 4x^2 + 23x + 15 = 0, D) 4x^2 - 23x + 15 = 0.

Solution

To solve this problem, we need to determine the quadratic equation in the form ax2+bx+c=0ax^2 + bx + c = 0 with the given roots 34-\frac{3}{4} and 55.

Step 1: Use the relationship between roots and coefficients

For a quadratic equation ax2+bx+c=0ax^2 + bx + c = 0, the following relationships hold if the roots are r1r_1 and r2r_2:

  1. Sum of roots: r1+r2=bar_1 + r_2 = -\frac{b}{a}
  2. Product of roots: r1r2=car_1 \cdot r_2 = \frac{c}{a}

Here, the roots are r1=34r_1 = -\frac{3}{4} and r2=5r_2 = 5.

Compute the sum of the roots:

r1+r2=34+5=3+204=174.r_1 + r_2 = -\frac{3}{4} + 5 = \frac{-3 + 20}{4} = \frac{17}{4}.

Compute the product of the roots:

r1r2=(34)(5)=154.r_1 \cdot r_2 = \left(-\frac{3}{4}\right)(5) = -\frac{15}{4}.

Step 2: Construct the quadratic equation

Using these values, we can write the quadratic equation as: ax2+bx+c=0whereb=a(r1+r2)andc=a(r1r2).a \cdot x^2 + b \cdot x + c = 0 \quad \text{where} \quad b = -a(r_1 + r_2) \quad \text{and} \quad c = a(r_1 \cdot r_2).

Let a=4a = 4 (since all the options use 4x24x^2): b=4174=17,c=4(154)=15.b = -4 \cdot \frac{17}{4} = -17, \quad c = 4 \cdot \left(-\frac{15}{4}\right) = -15.

Thus, the equation becomes: 4x217x15=0.4x^2 - 17x - 15 = 0.

Step 3: Match with the given options

The correct answer is: A) 4x217x15=04x^2 - 17x - 15 = 0.


Would you like a more detailed explanation or have further questions?

Related Questions:

  1. How do you verify the roots of a quadratic equation?
  2. What is the discriminant of a quadratic equation, and how is it used?
  3. How would the equation change if one root were doubled?
  4. What happens to the sum and product of roots if the coefficient aa changes?
  5. How do you factorize a quadratic equation into its root form?

Tip:

For quadratic equations, always double-check the sum and product of roots to ensure correctness!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Roots of Equations

Formulas

Sum of roots: r1 + r2 = -b/a
Product of roots: r1 * r2 = c/a
General quadratic equation: ax^2 + bx + c = 0

Theorems

Relationships between roots and coefficients of quadratic equations

Suitable Grade Level

Grades 8-10