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Revision Guide
Real Numbers encompass all rational and irrational numbers, forming a complete and continuous number line essential for various mathematical concepts.
Real Numbers - Quick Look Revision Guide
Your 1-page summary of the most exam-relevant takeaways from Mathematics.
This compact guide covers 20 must-know concepts from Real Numbers aligned with Class X preparation for Mathematics. Ideal for last-minute revision or daily review.
Key Points
Euclid’s division algorithm: For any two positive integers a & b, there exist unique integers q & r.
Euclid’s division algorithm states that for any two positive integers a and b, there exist unique integers q (quotient) and r (remainder) such that a = bq + r, where 0 ≤ r < b. This is fundamental for finding HCF.
Fundamental Theorem of Arithmetic: Every composite number can be expressed as a product of primes uniquely.
This theorem asserts that every composite number can be factorized into primes in a unique way, disregarding the order. It's crucial for understanding the structure of numbers.
HCF is the product of the smallest power of each common prime factor.
To find HCF of two numbers, identify all common prime factors and take the smallest power of each. For example, HCF of 12 (2²×3) and 18 (2×3²) is 2×3 = 6.
LCM is the product of the greatest power of each prime factor.
LCM is found by taking the highest power of all primes present in the numbers. For 12 (2²×3) and 18 (2×3²), LCM is 2²×3² = 36.
HCF(a,b) × LCM(a,b) = a × b.
This relationship allows calculating LCM if HCF is known and vice versa, simplifying computations for large numbers.
√2 is irrational: Cannot be expressed as a fraction of integers.
Proof by contradiction shows √2 cannot be written as a/b where a and b are coprime integers, highlighting numbers beyond fractions.
Prime factorization method for HCF & LCM.
Break down numbers into prime factors to systematically determine HCF and LCM, essential for solving problems efficiently.
Irrational numbers have non-terminating, non-repeating decimal expansions.
Unlike rationals, irrationals like √2 or π cannot be exactly expressed as fractions, with decimals that don’t terminate or repeat.
Sum/product of rational and irrational is irrational.
Adding or multiplying a non-zero rational with an irrational number always results in an irrational number, a key property for proofs.
Terminating decimals have denominators with only 2 and/or 5 as prime factors.
A rational number p/q in simplest form has a terminating decimal if q's prime factors are only 2 or 5, linking factorization to decimal behavior.
Non-terminating repeating decimals: Denominators have primes other than 2 or 5.
If q in p/q (simplest form) has prime factors beyond 2 or 5, the decimal expansion is non-terminating but repeating.
Proof of irrationality for √3, √5 similar to √2.
Using contradiction, assume √3 or √5 is rational, leading to a contradiction about the nature of primes, proving their irrationality.
Application of Euclid’s algorithm to find HCF.
Repeated application of Euclid’s division lemma simplifies finding HCF of large numbers without full factorization.
Composite numbers: Products of primes.
Every composite number is a product of primes, emphasizing primes as building blocks of numbers.
Uniqueness of prime factorization.
The Fundamental Theorem guarantees that aside from order, the prime factors of a number are unique, a cornerstone of number theory.
Rational numbers: Expressed as p/q, q≠0.
Rationals include all integers, fractions, and terminating or repeating decimals, forming a dense set on the number line.
Distinction between rational and irrational numbers.
Rationals can be expressed as fractions; irrationals cannot. This distinction is vital for understanding real numbers' completeness.
Use of factor trees for prime factorization.
Factor trees visually break down numbers into primes, aiding in understanding and computing HCF and LCM.
Example: Proving 7 × 11 × 13 + 13 is composite.
Factorizing 13(7×11 + 1) shows it’s a product of primes, hence composite, illustrating number properties.
Memory hack: HCF is 'highest common', LCM is 'least common'.
Remember HCF finds the highest factor common to numbers, while LCM finds the smallest multiple common to them, aiding quick recall.
Explore the world of Polynomials, understanding their types, degrees, and operations to solve algebraic expressions and equations effectively.
Explore the methods to solve a pair of linear equations in two variables, including graphical, substitution, elimination, and cross-multiplication techniques.
Explore the world of quadratic equations, learning to solve them using various methods like factoring, completing the square, and the quadratic formula.
A chapter that explores sequences where each term after the first is obtained by adding a constant difference, focusing on their properties, nth term, and sum formulas.
