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BAC1 ss · Mathematics
Numbers · Real numbers

Powers with rational exponents. Radicals

When a population-growth or compound-interest formula needs you to find "what annual rate is equivalent to a 20 % rise over 3 years", a root appears. Understanding radicals as powers with fractional exponents lets you handle them with the same rules you already know for powers.

Before you start, make sure you know: Properties of powers (4th ESO)
Before you start, make sure you know: Taking out factors (3rd ESO)

Radicals as powers with fractional exponents

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In the study of microorganisms, the size of certain structures can be expressed using powers and roots. Convert the following radicals into powers with fractional…

In the study of microorganisms, the size of certain structures can be expressed using powers and roots. Convert the following radicals into powers with fractional exponents and vice versa:

  1. a) $\sqrt[5]{x^2}$
  1. b) $\frac{1}{\sqrt[3]{a}}$
  1. c) $7^{\frac{3}{4}}$
  1. d) $x^{-\frac{1}{2}}$
Solve
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Simplify the following radicals by dividing the index and the exponent of the radicand by their highest common factor: a) $\sqrt[12]{x^8}$ b) $\sqrt[9]{27}$ c)…

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

  1. a) $\sqrt[12]{x^8}$
  1. b) $\sqrt[9]{27}$
  1. c) $\sqrt[10]{a^{15}}$
  1. d) $\sqrt[6]{125}$
Solve

From a fractional exponent to a radical, and back

Two-way equivalence diagram between the power $x^{2/3}$ and the radical $\sqrt[3]{x^2}$, showing that the numerator is the inner exponent and the denominator is the index. x^(2/3) ⇄ ∛x² numerator = exponent inside the root denominator = index of the root
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To optimise space in a graphic design, a programmer needs to extract factors from the radicals whenever possible. Extract factors from the radicals in the following…

To optimise space in a graphic design, a programmer needs to extract factors from the radicals whenever possible. Extract factors from the radicals in the following expressions:

  1. a) $\sqrt{50}$
  1. b) $\sqrt[3]{16x^5}$
  1. c) $\sqrt{a^3 b^4 c}$
  1. d) $\sqrt[4]{32}$
Solve
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In some financial formulas, it is preferable to have all elements under a single radical sign. Insert the factors inside the root and simplify the result: a) $3\sqrt{2}$…

In some financial formulas, it is preferable to have all elements under a single radical sign. Insert the factors inside the root and simplify the result:

  1. a) $3\sqrt{2}$
  1. b) $x^2 \sqrt[3]{x}$
  1. c) $\frac{2}{3}\sqrt{5}$
  1. d) $a \sqrt[4]{a^3}$
Solve
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Express the following powers with rational exponents in radical form and simplify the result by taking out as many factors as possible: a) $27^{\frac{2}{3}}$ b)…

Express the following powers with rational exponents in radical form and simplify the result by taking out as many factors as possible:

  1. a) $27^{\frac{2}{3}}$
  1. b) $125^{-\frac{1}{3}}$
  1. c) $\left(\frac{16}{81}\right)^{\frac{3}{4}}$
  1. d) $x^{1,5}$
Solve

Simplifying: taking out factors

Breaking down and taking out the factor $36$ as $6^2$ to simplify the radical $\sqrt{72}$ to $6\sqrt{2}$. √72 = √(36·2) = 6√2 36 is the largest perfect square that divides 72
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An architect is calculating the perimeters of a metal structure made up of several sections. Add and simplify the following like radicals to obtain the total length:…

An architect is calculating the perimeters of a metal structure made up of several sections. Add and simplify the following like radicals to obtain the total length:

$2\sqrt{27} - 5\sqrt{3} + \sqrt{12}$

Solve
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Calculate and simplify the following expression, leaving the result as a single radical with the smallest possible index: $$\frac{\sqrt[3]{a^2} \cdot…

Calculate and simplify the following expression, leaving the result as a single radical with the smallest possible index:

$$\frac{\sqrt[3]{a^2} \cdot \sqrt[4]{a^3}}{\sqrt[6]{a^5}}$$
Solve
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An architectural firm is designing a triangular garden. The lengths of the three paths bordering the garden are given by the following expressions in metres: Path A:…

An architectural firm is designing a triangular garden. The lengths of the three paths bordering the garden are given by the following expressions in metres:

  • Path A: $3\sqrt{20}$

  • Path B: $\sqrt{125}$

  • Path C: $2\sqrt{45}$

Calculate the total perimeter of the garden, simplifying the expression as far as possible.

Camino B: √125 m Camino A 3√20 m Camino C 2√45 m
Solve

Reducing the index of a radical

Step-by-step reduction of the index of $\sqrt[6]{x^4}$ to $\sqrt[3]{x^2}$ by simplifying the exponent fraction $4/6$ by its highest common factor. ⁶√x⁴ = x^(4/6) = x^(2/3) = ∛x² simplify the fraction 4/6 by its HCF (2) → index 3 instead of 6
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Simplify the following expression by reducing to a single radical and taking out factors if necessary: $$\sqrt{x \cdot \sqrt[3]{x^2 \cdot \sqrt{x}}}$$

Simplify the following expression by reducing to a single radical and taking out factors if necessary:

$$\sqrt{x \cdot \sqrt[3]{x^2 \cdot \sqrt{x}}}$$
Solve
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Simplify the following algebraic expression by operating with the radicals and taking out as many factors as possible. Express the final result using a single radical:…

Simplify the following algebraic expression by operating with the radicals and taking out as many factors as possible. Express the final result using a single radical:

$\displaystyle \frac{\sqrt{x^3 \cdot \sqrt[3]{x^2 \cdot y}}}{\sqrt[6]{x \cdot y^5}} \cdot \left( \frac{x}{y^2} \right)^{-1/2}$

² x³ · ³ x² · y ⁶ x · y⁵ x y² ⁻¹/² 2 × 3 = 6 PROPERTIES n aᵐ = a m n (a/b)⁻ⁿ = (b/a)ⁿ
Solve

Applications: equivalent growth rates

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Calculate the exact total surface area of a regular octahedron (formed by two square-based pyramids joined at their base) whose edge length is $\sqrt{6} + \sqrt{2}$ cm.…

Calculate the exact total surface area of a regular octahedron (formed by two square-based pyramids joined at their base) whose edge length is $\sqrt{6} + \sqrt{2}$ cm. You must leave the result simplified in radical form, without using decimal approximations.

(Hint: The area of an equilateral triangle of side length $a$ is $A = \frac{\sqrt{3}}{4}a^2$)

Solve
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Rationalise and simplify the following expression as far as possible. Ensure that the final denominator is an integer:…

Rationalise and simplify the following expression as far as possible. Ensure that the final denominator is an integer:

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

Solve

Summary

See all the exercises in this section