How Do You Simplify and Solve Surds in Maths?
The concept of surds plays a key role in mathematics and is widely applicable to both real-life situations and exam scenarios. Surds are essential when dealing with roots that cannot be simplified to rational numbers, making them vital for students in competitive exams, school mathematics, and practical problem-solving.
What Is Surds?
A surd is defined as an irrational root that cannot be expressed exactly as a fraction or terminating/repeating decimal. For example, numbers like √2, √7, or ∛5 are all surds because their decimal expansions are non-terminating and non-recurring. You’ll find this concept applied in areas such as irrational numbers, square roots, and indices and surds.
Key Formula for Surds
Here are some standard surds formulas and properties used for simplification:
- √a × √b = √(a × b)
- √a ÷ √b = √(a ÷ b)
- p√r ± q√r = (p ± q)√r
- To rationalise: \( \frac{1}{a+\sqrt{b}} = \frac{a-\sqrt{b}}{a^2 - b} \)
Cross-Disciplinary Usage
Surds are not only useful in Maths but also play an important role in Physics, Computer Science, and daily logical reasoning. For instance, calculating the diagonal of a square (using √2 × side), trigonometric ratios (like sin 60° = √3/2), and analyzing roots in quadratic equations often require surds. Students preparing for JEE or NEET will see surds in various questions.
Types of Surds
Surds can be classified into six main types:
- Simple Surd: Only one irrational number under a root, e.g., √3
- Pure Surd: No rational factor multiplied, e.g., √7
- Similar Surds: Surds with the same root part, e.g., 2√5 and 7√5
- Mixed Surd: Product of a rational and a surd, e.g., 5√2
- Compound Surd: Sum or difference of surds, e.g., √3 + √5
- Binomial Surd: Two surds combined (often for rationalisation): (√2 + √3)
Step-by-Step Illustration
- Simplify √72 into its simplest surd form.
1. Find the largest perfect square that divides 72: 72 = 36 × 2.
2. Split the root: √72 = √36 × √2
3. Calculate: √36 = 6
4. Final answer: 6√2
Operations with Surds
You can add or subtract surds only if they are like surds (same number under the root). For multiplication and division, follow the surd laws.
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Add: 3√2 + 5√2 = (3 + 5)√2 = 8√2
- Multiply: 2√3 × 4√6 = 2 × 4 × √3 × √6 = 8 × √18 = 8 × 3√2 = 24√2
Speed Trick or Vedic Shortcut
Here’s a quick shortcut for multiplying surds: If you get two similar surds in an exam (like √a × √a), simply write it as a.
Example Trick: √3 × √3 = 3 | √5 × √20 = √(5×20) = √100 = 10
This speed tip helps in MCQs and board exams. Vedantu’s live classes include many such tips to boost your performance.
Try These Yourself
- Simplify √50.
- Add 2√3 and 5√3.
- Is √9 a surd? Why or why not?
- Rationalize the denominator: \( \frac{2}{\sqrt{5}} \)
Frequent Errors and Misunderstandings
- Trying to add unlike surds: e.g., 2√2 + 3√3 ≠ 5√5
- Forgetting to rationalise the denominator properly
- Confusing rational and irrational roots: √16 = 4 is not a surd
Relation to Other Concepts
The idea of surds connects closely with topics such as laws of exponents and irrational numbers. Mastering this helps with understanding indices, logarithms, and simplification of algebraic expressions in future chapters.
Classroom Tip
A quick way to remember surds: “If a root cannot be reduced to a rational number, it’s a surd.” Also, after factorising, always check for perfect squares to take out of the root sign. Vedantu’s teachers use visual aids for this rule in live classes.
We explored surds—from definition, formula, examples, mistakes, and connections to other subjects. Continue practicing with Vedantu to become confident in solving problems using this concept.
Further Reading & Related Topics:
