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Prep 1 · Mathematics
Numbers · Powers, roots and logarithms

Properties of Radicals and Rationalization

Before you start, make sure you know: Special products (Secondary Year 2)
Before you start, make sure you know: Extracting factors (Secondary Year 3)

Ximena calculates the area of a board and gets $\dfrac{\sqrt2}{\sqrt3+\sqrt2}$. It is a result that is hard to use, and also $5\sqrt3 - 2\sqrt3$ can be reduced to a single term. Here you will learn to write any expression with radicals in its simplest form.

Simplifying: Extracting Factors and Reducing the Index

Step-by-step diagram of extracting factors from the square root of 72, factoring it as 36 times 2 until reaching 6 square root of 2 √72 perfect square: 36 · 2 = √(36·2) √36 = 6 comes out of the root = 6√2 36 is the largest perfect square that divides 72
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Take out as many factors as possible from the following radicals: a) $\sqrt{72}$ b) $\sqrt[3]{250}$

Take out as many factors as possible from the following radicals:

  1. a) $\sqrt{72}$
  2. b) $\sqrt[3]{250}$
Solve
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Insert the integer factors into the radical and simplify if possible: a) $3 \sqrt{5}$ b) $2 \sqrt[4]{3}$

Insert the integer factors into the radical and simplify if possible:

  1. a) $3 \sqrt{5}$
  2. b) $2 \sqrt[4]{3}$
Solve
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Simplify the following radicals by dividing the index and the exponent by their highest common factor: a) $\sqrt[6]{27}$ b) $\sqrt[8]{16}$

Simplify the following radicals by dividing the index and the exponent by their highest common factor:

  1. a) $\sqrt[6]{27}$
  2. b) $\sqrt[8]{16}$
Solve
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Express as a single radical and simplify the result: a) $\sqrt{\sqrt[3]{64}}$ b) $\left(\sqrt[3]{\sqrt{2}}\right)^6$

Express as a single radical and simplify the result:

  1. a) $\sqrt{\sqrt[3]{64}}$
  2. b) $\left(\sqrt[3]{\sqrt{2}}\right)^6$
Solve
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Take out as many factors as possible from the following root and simplify the resulting expression: $\sqrt[3]{\frac{81 x^4 y^7}{16 z^5}}$

Take out as many factors as possible from the following root and simplify the resulting expression:

$\sqrt[3]{\frac{81 x^4 y^7}{16 z^5}}$

Solve

Adding and Subtracting Like Radicals

Two radicals are like radicals if they have the same index and the same radicand. They can only be added or subtracted if they are like radicals, just like like terms in algebra.

Step-by-step diagram of adding like radicals by extracting factors from the square root of 50 and the square root of 18 to reduce them to the square 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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Perform the following additions and subtractions of like radicals: a) $5\sqrt{3} - 2\sqrt{3} + 4\sqrt{3}$ b) $\frac{1}{2}\sqrt{7} + \frac{3}{2}\sqrt{7} - \sqrt{7}$

Perform the following additions and subtractions of like radicals:

  1. a) $5\sqrt{3} - 2\sqrt{3} + 4\sqrt{3}$
  2. b) $\frac{1}{2}\sqrt{7} + \frac{3}{2}\sqrt{7} - \sqrt{7}$
Solve
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Perform the following operation, first taking out the necessary factors so that the radicals are like terms: $3\sqrt{50} + 2\sqrt{18} - \sqrt{8}$

Perform the following operation, first taking out the necessary factors so that the radicals are like terms:

$3\sqrt{50} + 2\sqrt{18} - \sqrt{8}$

Solve
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Show, by expanding the algebraic identities and simplifying, that the result of the following expression is an integer:…

Show, by expanding the algebraic identities and simplifying, that the result of the following expression is an integer:

$(\sqrt{7} - \sqrt{3})^2 + (\sqrt{7} + \sqrt{3})^2$

Solve

Multiplying and Dividing with Different Indices

Diagram of multiplying the square root of 2 by the cube root of 3, reducing to a common index of 6 using fractional exponents √2 · ∛3 rewrite as powers = 2^(3/6) · 3^(2/6) common denominator 6: one radical = ⁶√(2³·3²) same index (6): now they can be combined

With the same index, you operate directly on the radicand: $\sqrt[n]{a}\cdot\sqrt[n]{b}=\sqrt[n]{ab}$. With different indices, first reduce to a common index (rewrite the fractions of the exponents with the same denominator).

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Perform the following multiplications of radicals with the same index and take out factors if possible: a) $\sqrt{2} \times \sqrt{8}$ b) $\sqrt[3]{4} \times \sqrt[3]{10}$

Perform the following multiplications of radicals with the same index and take out factors if possible:

  1. a) $\sqrt{2} \times \sqrt{8}$
  2. b) $\sqrt[3]{4} \times \sqrt[3]{10}$
Solve
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Reduce to a common index and perform the following multiplication and division of radicals: $\frac{\sqrt{2} \times \sqrt[3]{3}}{\sqrt[6]{6}}$

Reduce to a common index and perform the following multiplication and division of radicals:

$\frac{\sqrt{2} \times \sqrt[3]{3}}{\sqrt[6]{6}}$

Solve
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Simplify the following expression by inserting the factors into the innermost radical and expressing it as a single root: $\sqrt{2 \times \sqrt[3]{2}}$

Simplify the following expression by inserting the factors into the innermost radical and expressing it as a single root:

$\sqrt{2 \times \sqrt[3]{2}}$

Solve
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Simplify the following expression with nested radicals, expressing the result as a single root: $\sqrt{2 \times \sqrt[3]{4 \times \sqrt{8}}}$

Simplify the following expression with nested radicals, expressing the result as a single root:

$\sqrt{2 \times \sqrt[3]{4 \times \sqrt{8}}}$

Solve

Rationalizing Denominators

Leaving a root in the denominator is not "wrong," but it is not the standard form: we rationalize by multiplying the top and bottom by whatever is needed so that the denominator has no roots.

Step-by-step diagram of rationalizing a monomial denominator and a binomial denominator by multiplying by its conjugate 6√3 · √3√3 = 6√33 = 2√3 monomial denominator: multiply top and bottom by the same root 4√5−1 · √5+1√5+1 multiply by the conjugate: (√5−1)(√5+1) = 5−1 = 4
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Rationalise the denominator of the following fractions and simplify the result: a) $\frac{6}{\sqrt{3}}$ b) $\frac{10}{\sqrt{5}}$

Rationalise the denominator of the following fractions and simplify the result:

  1. a) $\frac{6}{\sqrt{3}}$
  2. b) $\frac{10}{\sqrt{5}}$
Solve
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Rationalise the following expressions by multiplying by the conjugate of the denominator: a) $\frac{4}{\sqrt{5}-1}$ b) $\frac{2}{\sqrt{3}+1}$

Rationalise the following expressions by multiplying by the conjugate of the denominator:

  1. a) $\frac{4}{\sqrt{5}-1}$
  2. b) $\frac{2}{\sqrt{3}+1}$
Solve
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Rationalise the following fractions with roots of index greater than 2: a) $\frac{10}{\sqrt[5]{8}}$ b) $\frac{3}{\sqrt[4]{27}}$

Rationalise the following fractions with roots of index greater than 2:

  1. a) $\frac{10}{\sqrt[5]{8}}$
  2. b) $\frac{3}{\sqrt[4]{27}}$
Solve
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Rationalise the denominator and simplify the following expression as much as possible: $\frac{\sqrt{2}}{\sqrt{3}+\sqrt{2}}$

Rationalise the denominator and simplify the following expression as much as possible:

$\frac{\sqrt{2}}{\sqrt{3}+\sqrt{2}}$

Solve
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Perform the following combined operation with irrational fractions. To do so, first rationalise each fraction separately and then perform the subtraction:…

Perform the following combined operation with irrational fractions. To do so, first rationalise each fraction separately and then perform the subtraction:

$\frac{2}{\sqrt{5}-\sqrt{3}} - \frac{2}{\sqrt{5}+\sqrt{3}}$

Solve
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Rationalise the denominator of the following fraction and simplify as much as possible by working out the numerator: $\frac{\sqrt{6}-\sqrt{2}}{\sqrt{6}+\sqrt{2}}$

Rationalise the denominator of the following fraction and simplify as much as possible by working out the numerator:

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

Solve

Applications in Geometry and Physics

Isosceles triangle with equal sides of square root of 15, base square root of 6, and height h drawn with a dashed line base = √6 √15 √15 h

When an exact measurement involves roots, we operate with radicals and leave the result simplified: this way no precision is lost.

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In a carpentry workshop, a rectangular board with exact dimensions of $\sqrt{12}$ dm wide and $\sqrt{27}$ dm long is going to be cut. Calculate the area and perimetre of…

In a carpentry workshop, a rectangular board with exact dimensions of $\sqrt{12}$ dm wide and $\sqrt{27}$ dm long is going to be cut. Calculate the area and perimetre of the board, expressing the results in exact form using simplified radicals.

Solve
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The speed $v$ (in m/s) of a wave travelling along a stretched string is calculated using the formula $v = \sqrt{\frac{F}{\mu}}$, where $F$ is the tension in newtons and…

The speed $v$ (in m/s) of a wave travelling along a stretched string is calculated using the formula $v = \sqrt{\frac{F}{\mu}}$, where $F$ is the tension in newtons and $\mu$ the linear density in kg/m. If a guitar string is subjected to a tension of $F = 12$ N and has a density of $\mu = 5$ kg/m, find the exact value of $v$. Rationalise the denominator and take out any possible factors.

Solve
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Calculate the exact length of the main diagonal $D$ of a cube with an edge length of $a = \sqrt{5}$ cm. Remember that the diagonal of a cube is calculated as…

Calculate the exact length of the main diagonal $D$ of a cube with an edge length of $a = \sqrt{5}$ cm. Remember that the diagonal of a cube is calculated as $D = \sqrt{a^2 + a^2 + a^2}$. Express the result in the most simplified form possible.

D = ? a a a
Solve
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In graphic design, proportions based on the golden ratio $\phi = \frac{1+\sqrt{5}}{2}$ are considered aesthetically perfect. A canvas has the shape of a golden rectangle…

In graphic design, proportions based on the golden ratio $\phi = \frac{1+\sqrt{5}}{2}$ are considered aesthetically perfect. A canvas has the shape of a golden rectangle (the quotient of its longer side and its shorter side is $\phi$). If the shorter side of the canvas measures exactly $\sqrt{5}-1$ meters, calculate the exact length of the longer side. Simplify the result as much as possible.

Solve
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The front wall of a cabin is in the shape of an isosceles triangle. The base of the triangle measures $\sqrt{6}$ meters and the two equal sides measure $\sqrt{15}$…

The front wall of a cabin is in the shape of an isosceles triangle. The base of the triangle measures $\sqrt{6}$ meters and the two equal sides measure $\sqrt{15}$ meters each. Calculate the exact value of the height $h$ perpendicular to the base and the total area of the front wall. Rationalize the results if roots appear in the denominator.

b = √6 √15 √15 h
Solve
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In physics, the speed $v$ of an object can be rearranged from its kinetic energy $E_c$ and its mass $m$ using the formula $v = \sqrt{\frac{2E_c}{m}}$. If a prototype…

In physics, the speed $v$ of an object can be rearranged from its kinetic energy $E_c$ and its mass $m$ using the formula $v = \sqrt{\frac{2E_c}{m}}$. If a prototype vehicle has a mass of $m = \sqrt{3}$ kg and its kinetic energy is $E_c = 45$ J, calculate the exact value of its speed. Rationalise and take out any possible factors from the resulting root.

Solve

Back to the beginning: rationalizing with the conjugate, $\dfrac{\sqrt2}{\sqrt3+\sqrt2} = \dfrac{\sqrt2(\sqrt3-\sqrt2)}{(\sqrt3+\sqrt2)(\sqrt3-\sqrt2)} = \dfrac{\sqrt6-2}{3-2} = \sqrt6 - 2$, and subtracting like radicals gives $5\sqrt3 - 2\sqrt3 = 3\sqrt3$.

Summary

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