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Real numbers · Real numbers

Radicals

In engineering and physics, radicals are not an algebraic whim: they appear in the speed of a wave, the period of a pendulum or the diagonal of a component. Mastering them with fractional exponents, instead of loose "recipes", lets you manipulate any expression with confidence.

Before you start, make sure you know: Powers with rational exponents. Radicals (4th ESO)
Before you start, make sure you know: Properties of radicals and rationalisation (4th ESO)

Radicals as fractional exponents

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Express as a power with a fractional index and simplify fully the expression $\sqrt[6]{x^4 y^2 z^8}$, assuming that all variables represent positive real numbers.

Express as a power with a fractional index and simplify fully the expression $\sqrt[6]{x^4 y^2 z^8}$, assuming that all variables represent positive real numbers.

Solve
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Determine whether the radicals $\sqrt[4]{25x^2}$ and $\sqrt{5x}$ are equivalent for any value of $x > 0$. Justify your method using fractional indices.

Determine whether the radicals $\sqrt[4]{25x^2}$ and $\sqrt{5x}$ are equivalent for any value of $x > 0$. Justify your method using fractional indices.

Solve

Simplifying: extracting factors and reducing the index

Decomposition of the square root of 72 into the square root of 36 times 2 to extract the factor 6 and obtain 6 square root of 2. √72 = √(36·2) = 6√2 36 is the largest perfect square that divides 72
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Take out as many factors as possible from inside the following radical, simplifying the expression fully: $\sqrt[3]{108 a^5 b^7 c^3}$.

Take out as many factors as possible from inside the following radical, simplifying the expression fully: $\sqrt[3]{108 a^5 b^7 c^3}$.

Solve
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Simplify the following expression by applying the root of a root property and expressing the result with a single radical: $\sqrt[3]{a^2 \sqrt{a}}$.

Simplify the following expression by applying the root of a root property and expressing the result with a single radical: $\sqrt[3]{a^2 \sqrt{a}}$.

Solve

Operations: like radicals and different indices

Step-by-step working of an addition and subtraction of radicals by extracting common factors with 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 additions and subtractions of the following like radicals, first extracting factors to simplify the result: $5\sqrt{18} - 2\sqrt{50} + \sqrt{8}$.

Perform the additions and subtractions of the following like radicals, first extracting factors to simplify the result: $5\sqrt{18} - 2\sqrt{50} + \sqrt{8}$.

Solve
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Carry out the following mixed operation with radicals of different indices, expressing the final result as a single simplified radical:…

Carry out the following mixed operation with radicals of different indices, expressing the final result as a single simplified radical: $\frac{\sqrt{2x} \cdot \sqrt[3]{4x^2}}{\sqrt[6]{8x^5}}$.

Solve

Rationalising denominators

Step-by-step examples of rationalisation: monomial, multiplying by the root of the denominator, and binomial, multiplying numerator and denominator by the conjugate. 6 √3 · √3 √3 = 6√3 3 = 2√3 monomial denominator: multiply by the same root above and below 4 √5−1 · √5+1 √5+1 conjugate: (√5−1)(√5+1) = 5−1 = 4
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Rationalise the denominator of the following expression and simplify the final result, extracting factors if possible: $\frac{6x}{\sqrt[5]{8x^2y^3}}$.

Rationalise the denominator of the following expression and simplify the final result, extracting factors if possible: $\frac{6x}{\sqrt[5]{8x^2y^3}}$.

Solve
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Rationalise the denominator by multiplying by the conjugate expression and simplify by expanding the numerator: $\frac{2\sqrt{3} - \sqrt{2}}{\sqrt{3} + 2\sqrt{2}}$.

Rationalise the denominator by multiplying by the conjugate expression and simplify by expanding the numerator: $\frac{2\sqrt{3} - \sqrt{2}}{\sqrt{3} + 2\sqrt{2}}$.

Solve
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Rationalise the denominator of the following fraction containing three radical terms and simplify the final result: $\frac{4}{\sqrt{2} + \sqrt{3} - \sqrt{5}}$.

Rationalise the denominator of the following fraction containing three radical terms and simplify the final result: $\frac{4}{\sqrt{2} + \sqrt{3} - \sqrt{5}}$.

Solve

Applications in geometry and physics

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The period $T$ of a simple pendulum is given by the physics formula $T = 2\pi\sqrt{\frac{L}{g}}$, where $L$ is the length of the string and $g$ is acceleration due to…

The period $T$ of a simple pendulum is given by the physics formula $T = 2\pi\sqrt{\frac{L}{g}}$, where $L$ is the length of the string and $g$ is acceleration due to gravity. If an engineer needs the new period to be exactly $\sqrt{2} + 1$ times the original period, by what exact factor must they multiply the original length $L$? Express your reasoning algebraically by expanding the square of the binomial.

Solve
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In a rectangular prism, the lengths of its three concurrent edges measure exactly $\sqrt{2}$ m, $\sqrt{3}$ m and $\sqrt{5}$ m. Calculate the exact value of the space…

In a rectangular prism, the lengths of its three concurrent edges measure exactly $\sqrt{2}$ m, $\sqrt{3}$ m and $\sqrt{5}$ m. Calculate the exact value of the space diagonal of the prism ($D = \sqrt{a^2 + b^2 + c^2}$) and its volume, expressing both results in their simplest radical form.

Solve
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According to Kleiber's Law in biology, the basal metabolic rate $R$ of a mammal scales with its body mass $M$ according to the relationship $R = k \sqrt[4]{M^3}$, where…

According to Kleiber's Law in biology, the basal metabolic rate $R$ of a mammal scales with its body mass $M$ according to the relationship $R = k \sqrt[4]{M^3}$, where $k$ is a constant. If animal $A$ has a mass exactly $27$ times greater than that of animal $B$, determine the exact ratio $\frac{R_A}{R_B}$ using properties of radicals and extracting factors.

Solve

Summary

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