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1800-102-2727The word surd comes from the Latin word surdus, meaning deaf or mute. In the early days of mathematics, Arabians used to consider irrational numbers as mute. This means there was no value in these irrational numbers. Only rational numbers were considered audible. Over time, surds became a vital part of today’s mathematics.
Surds represent those numbers that do not have roots. For example, 4, 25, 36 have proper roots as 2, 5, and 6, whereas numbers 7, 12, 20 do not. These improper numbers, which do not have proper roots, are termed as surds.
These surds can be represented with exponential powers with fractional powers as well, like √6=6¹/², √2=2¹/².
We can represent surds in the simplified way by taking out the roots of the number. A pure surd will then become a mixed surd.
e.g. √50 = √(5×5×2) = 5√2
Solve 16³/² + 16-³/² = ?
Solution – We know from the law of exponents,
aᵐ x aⁿ = aᵐ⁺ⁿ
a-ᵐ = 1/aᵐ
⇒16³/² + 1/16³/²
⇒(16¹/²)³ + 1/(16¹/²)³
⇒(4²*¹/²)³ + 1/(4²*¹/²)³
⇒4³ + 1/4³
⇒ 64 + 1/64
⇒ (64 x 64+ 1)/64
= (4096+1)/64
= 4097/64
Rationalise 1/[(8√11 )- (7√5)]
Solution – We know that the conjugate of (8√11 ) - (7√5) is (8√11 )+(7√5). Change the addition sign in the expression and vice versa to find the conjugate of an expression.
To rationalize the denominator of the given fraction, we need to multiply the conjugate of the denominator on both numerator and denominator.
= [1/[(8√11 ) - (7√5)]] × [[(8√11 ) + (7√5)]/[(8√11 ) + (7√5)]]
= [(8√11 ) + (7√5)]/[(8√11 )² - (7√5)²]
= [(8√11 ) + (7√5)]/[704- 245]
= [(8√11 ) + (7√5)]/459
Fun fact: Surds was invented by a European mathematician, Gherardo of Cremona, in 1150 BC. He used the Pythagoras theorem to find the diagonal of a square and the value of the first surd. He termed this value ‘voiceless’ because the root value had no meaning at that time.