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BAC1 ss · Mathematics
Numbers · Real numbers

Operations with radicals

You already know how to convert a radical into a fractional power and how to take factors out of it. Now it is time to combine them: to add them, multiply them and, above all, remove them from the denominator of a fraction so that the result is in the form expected in any exam or report.

Before you start, make sure you know: Special products (notable identities) (2nd ESO)
Before you start, make sure you know: Taking factors out of a radical (3rd ESO)

Like radicals: adding and subtracting

Step-by-step calculation of adding and subtracting like radicals after taking out factors: 3 root of 50 plus 2 root of 18 minus root of 8 gives 19 root of 2. 3√50 + 2√18 − √8 = 3·5√2 + 2·3√2 − 2√2 = 15√2 + 6√2 − 2√2 = 19√2
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Simplify the following mathematical expression by extracting factors from the radicals and grouping like terms: $5\sqrt{12} - \sqrt{27} + 2\sqrt{75}$

Simplify the following mathematical expression by extracting factors from the radicals and grouping like terms:

$5\sqrt{12} - \sqrt{27} + 2\sqrt{75}$

Solve
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A technology company is designing a new smartphone model. The screen is rectangular and its exact dimensions are given by the following radicals: the base measures…

A technology company is designing a new smartphone model. The screen is rectangular and its exact dimensions are given by the following radicals: the base measures $\sqrt{12}$ cm and the height measures $\sqrt{3}$ cm. Calculate the area of the screen, expressing the result in simplified form.

√12 cm √3 cm Area = ? √12 × √3
Solve

Multiplying and dividing radicals

Multiplication of radicals with different indices expressed as powers of base 2 with fractional exponents. ∛4 · √2 = 2^(2/3) · 2^(1/2) everything as powers of 2 = 2^(7/6) add the exponents: 2/3 + 1/2 = 7/6 = ⁶√2⁷ = 2·⁶√2 a 2 is taken out of the root
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Extract all possible factors from the following radicals to obtain the simplest expression: a) $\sqrt{72x^4y^3}$ b) $\sqrt[3]{128a^5}$

Extract all possible factors from the following radicals to obtain the simplest expression:

  1. a) $\sqrt{72x^4y^3}$
  1. b) $\sqrt[3]{128a^5}$
Solve
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Extract all possible factors from the following radicals and simplify the resulting expression to obtain a single term: $3\sqrt{80} - 2\sqrt{45} + \sqrt{20}$

Extract all possible factors from the following radicals and simplify the resulting expression to obtain a single term:

$3\sqrt{80} - 2\sqrt{45} + \sqrt{20}$

Solve

Rationalising the denominator: monomial and binomial

Rationalisation of a fraction with a square root in the denominator by multiplying the numerator and denominator by that root. 6 √3 · √3 √3 multiply the top and the bottom by √3 = 6√3 3 = 2√3 (6 ÷ 3 = 2)
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Rationalise the following fractions so that no radical remains in the denominator. Remember to simplify the final result if possible: a) $\frac{10}{\sqrt{2}}$ b)…

Rationalise the following fractions so that no radical remains in the denominator. Remember to simplify the final result if possible:

  1. a) $\frac{10}{\sqrt{2}}$
  1. b) $\frac{3}{\sqrt[3]{5}}$
Solve
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In the design of a new smartphone chip, one of the connections has a length given by the product of two radical components. Calculate the exact value of this length by…

In the design of a new smartphone chip, one of the connections has a length given by the product of two radical components. Calculate the exact value of this length by simplifying the following product and expressing it under a single radical:

$\sqrt[3]{a^2} \cdot \sqrt[4]{a^3}$

Solve
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Calculate the area of a square public square whose side measures $(2 + \sqrt{5})$ metres. Express the result in exact form, simplifying any radicals that appear when…

Calculate the area of a square public square whose side measures $(2 + \sqrt{5})$ metres. Express the result in exact form, simplifying any radicals that appear when expanding the binomial.

2² 2√5 2√5 (√5)² Side = 2 + √5 2 √5 2 √5
Solve

Rationalising a binomial denominator (conjugate)

Step-by-step rationalisation of a fraction with a binomial denominator by multiplying the numerator and denominator by its conjugate expression. 4 √5−1 · √5+1 √5+1 conjugate: (√5−1)(√5+1) = 5−1 = 4
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Rationalise the following expressions to eliminate the radicals from the denominator and simplify the final result: a) $\dfrac{6}{\sqrt[3]{9}}$ b) $\dfrac{10}{\sqrt{5}}$

Rationalise the following expressions to eliminate the radicals from the denominator and simplify the final result:

  1. a) $\dfrac{6}{\sqrt[3]{9}}$
  1. b) $\dfrac{10}{\sqrt{5}}$
Solve
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Simplify the following combined expression as much as possible, extracting factors from the radicals and rationalising any terms necessary to group the numerical part:…

Simplify the following combined expression as much as possible, extracting factors from the radicals and rationalising any terms necessary to group the numerical part:

$$3\sqrt{175} - \frac{5}{\sqrt{7}} + \sqrt[4]{441} - 2\sqrt{112}$$
Solve
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Rationalise and simplify the following fraction. You must work out the numerator after rationalising to obtain the simplest possible expression: $$\frac{2\sqrt{6} -…

Rationalise and simplify the following fraction. You must work out the numerator after rationalising to obtain the simplest possible expression:

$$\frac{2\sqrt{6} - 3\sqrt{2}}{2\sqrt{3} + \sqrt{2}}$$
Solve

Putting it all together: expressions with several radicals

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Reduce to a single radical and simplify the resulting expression, assuming that the variables $x$ and $y$ represent positive real values: $$\frac{\sqrt[3]{x^2 \cdot y}…

Reduce to a single radical and simplify the resulting expression, assuming that the variables $x$ and $y$ represent positive real values:

$$\frac{\sqrt[3]{x^2 \cdot y} \cdot \sqrt{x \cdot y^3}}{\sqrt[6]{x^5 \cdot y^4}}$$
Solve
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An architect is designing a triangular skylight for a new shopping centre. The design requires the base of the skylight to be an equilateral triangle whose height is…

An architect is designing a triangular skylight for a new shopping centre. The design requires the base of the skylight to be an equilateral triangle whose height is exactly $H = \sqrt{18} + \sqrt{6}$ metres. Calculate the exact value of the area of the skylight, expressing the result as a simplified radical in $m^2$.

H = √18 + √6 L L L
Solve

Summary

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