109 LearnersLast updated on August 5th, 2025
Subtraction of Roots of Quadratic Equation
The mathematical operation of finding the difference between the roots of a quadratic equation is known as the subtraction of roots of a quadratic equation. It helps to understand the relationship between the roots and coefficients and solve problems involving these roots.
What is Subtraction of Roots of Quadratic Equation?
Subtracting the roots of a quadratic equation involves finding the difference between the two roots of the equation.
A quadratic equation is generally represented as ax² + bx + c = 0, where a, b, and c are coefficients. The roots of the equation are determined using the quadratic formula: x = (-b ± √(b² - 4ac)) / (2a).
The subtraction of roots is simply the difference between these two roots.
How to Subtract Roots of Quadratic Equation?
When subtracting the roots of a quadratic equation, students should follow these steps:
1. Use the quadratic formula to find the roots: x₁ = (-b + √(b² - 4ac)) / (2a) and x₂ = (-b - √(b² - 4ac)) / (2a).
2. Calculate the difference: Subtract the second root from the first root.
3. Simplify the result: The expression simplifies to (2√(b² - 4ac)) / (2a), which can be further simplified as √(b² - 4ac) / a.
Methods to Subtract Roots of Quadratic Equation
The following are the methods for subtracting the roots of a quadratic equation:
Method 1: Direct Calculation
Using the quadratic formula, compute both roots and find their difference.
Example: For the quadratic equation 2x² - 4x + 2 = 0, find the roots and subtract them: Roots: x₁ = (4 + √0) / 4 and x₂ = (4 - √0) / 4, so the subtraction is x₁ - x₂ = 0.
Method 2: Discriminant Approach
Use the discriminant (b² - 4ac) to find the difference.
Example: For the equation x² - 5x + 6 = 0, the discriminant is 1. Thus, the subtraction of roots is √1 = 1.
Properties of Subtraction of Roots of Quadratic Equation
The subtraction of roots of a quadratic equation has specific properties, which include:
1. The subtraction is directly related to the discriminant: The difference between the roots is √(b² - 4ac) / a.
2. If the discriminant is zero, the roots are equal, and their subtraction is zero.
3. If the discriminant is positive, the roots are real and distinct, and the subtraction is non-zero.
4. If the discriminant is negative, the roots are complex conjugates, and their subtraction is imaginary.
5. The subtraction of roots is not commutative or associative.
Tips and Tricks for Subtraction of Roots of Quadratic Equation
The following tips and tricks can help students efficiently deal with the subtraction of roots of a quadratic equation:
Tip 1: Always check the discriminant first to determine the nature of the roots.
Tip 2: For complex roots, remember that the subtraction will yield an imaginary number.
Tip 3: Simplify the expression using the discriminant to avoid unnecessary calculations.
Tip 4: Use symmetry properties of quadratic equations to verify calculations.
Tip 5: Practice with different equations to become familiar with the process.
Ignoring the Discriminant
Students often overlook the discriminant, which determines the nature of the roots. Always compute the discriminant to guide the subtraction process.
Mistake 1
Incorrect Simplification
Errors can occur when simplifying the difference of roots; ensure correct simplification of radical expressions.
Mistake 2
Misinterpreting Complex Roots
When dealing with complex roots, students sometimes forget that the subtraction yields an imaginary result. Remember that complex roots occur in conjugate pairs.
Mistake 3
Neglecting Sign Changes
The sign in front of the square root in the quadratic formula affects the result. Double-check signs during subtraction.
Mistake 4
Overlooking Zero Discriminant
A zero discriminant means equal roots; students might attempt unnecessary calculations. Recognize this scenario to save time.
Mistake 5
Examples of Subtraction of Roots of Quadratic Equation
Find the subtraction of the roots of the equation x² - 4x + 3 = 0
2
Problem 1
Use the quadratic formula: x₁ = (4 + √(4² - 4*1*3)) / 2 = 3 x₂ = (4 - √(4² - 4*1*3)) / 2 = 1 Subtract the roots: x₁ - x₂ = 3 - 1 = 2
For the quadratic equation 3x² - 12x + 12 = 0, calculate the subtraction of the roots.
Explanation
0
Problem 2
Use the discriminant: b² - 4ac = 12² - 4*3*12 = 0 The roots are equal; hence, the subtraction is 0.
Compute the subtraction of the roots for 2x² - 6x + 5 = 0.
Explanation
√2
Problem 3
Find the discriminant: b² - 4ac = 6² - 4*2*5 = 4 The subtraction is √4/2 = √2.
Determine the subtraction of the roots of the equation x² + 2x + 5 = 0.
Explanation
2i
Problem 4
Compute the discriminant: b² - 4ac = 2² - 4*1*5 = -16 The roots are complex, and the subtraction is √(-16)/1 = 2i.
Find the subtraction of roots for the equation 4x² - 4x + 1 = 0.
Explanation
0
Yes, if the discriminant is negative, the roots are complex, and their subtraction is an imaginary number.
1.Does the subtraction of roots depend on the coefficients?
2.Is subtraction of roots commutative?
3.What happens if the discriminant is zero?
4.Can subtraction be applied to any quadratic equation?
5.How can children in Australia use numbers in everyday life to understand Subtraction of Roots of Quadratic Equation?
6.What are some fun ways kids in Australia can practice Subtraction of Roots of Quadratic Equation with numbers?
7.What role do numbers and Subtraction of Roots of Quadratic Equation play in helping children in Australia develop problem-solving skills?
8.How can families in Australia create number-rich environments to improve Subtraction of Roots of Quadratic Equation skills?
Common Mistakes and How to Avoid Them in Subtraction of Roots of Quadratic Equation
Subtracting the roots of a quadratic equation can be challenging due to common mistakes. Being aware of these errors can help students avoid them.
Explore More numbers
![Important Math Links Icon]()
Previous to Subtraction of Roots of Quadratic Equation
![Important Math Links Icon]()
Next to Subtraction of Roots of Quadratic Equation
Hiralee Lalitkumar Makwana
About the Author
Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.
Fun Fact
: She loves to read number jokes and games.
