Algebra II : Radicals

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #65 : Solving Radical Equations

Solve the equation:  \displaystyle \sqrt{x-9}+31 = 35

Possible Answers:

\displaystyle 13

\displaystyle 26

\displaystyle \textup{There is no solution.}

\displaystyle 25

\displaystyle 169

Correct answer:

\displaystyle 25

Explanation:

Subtract 31 from both sides of the equation.

\displaystyle \sqrt{x-9}+31-31 = 35-31

\displaystyle \sqrt{x-9}=4

Square both sides.

\displaystyle (\sqrt{x-9})^2=4^2

Simplify both sides.

\displaystyle x-9 =16

Add nine on both sides.

\displaystyle x-9 +9=16+9

The answer is:  \displaystyle 25

Example Question #66 : Solving Radical Equations

Solve the equation:  \displaystyle \sqrt[3]{3x-7}=4

Possible Answers:

\displaystyle \frac{57}{3}

\displaystyle \frac{57}{6}

\displaystyle \frac{131}{9}

\displaystyle \frac{71}{3}

\displaystyle \textup{No solution.}

Correct answer:

\displaystyle \frac{71}{3}

Explanation:

To eliminate the radical, we will have to cube both sides.

\displaystyle (\sqrt[3]{3x-7})^3=4^3

The equation becomes:

\displaystyle 3x-7=64

Add seven on both sides.

\displaystyle 3x=71

Divide by three on both sides.

\displaystyle \frac{3x}{3}=\frac{71}{3}

The answer is:  \displaystyle \frac{71}{3}

Example Question #67 : Solving Radical Equations

Solve:  \displaystyle 3\sqrt[4]{9-2x} = 1

Possible Answers:

\displaystyle \frac{364}{81}

\displaystyle \frac{1459}{162}

\displaystyle \frac{99}{2}

\displaystyle 45

\displaystyle -\frac{364}{81}

Correct answer:

\displaystyle \frac{364}{81}

Explanation:

Divide by three on both sides.

\displaystyle \frac{3\sqrt[4]{9-2x} }{3}= \frac{1}{3}

Rewrite the equation.

\displaystyle \sqrt[4]{9-2x} = \frac{1}{3}

Raise both sides to the fourth power.

\displaystyle (\sqrt[4]{9-2x})^4 =( \frac{1}{3})^4

Simplify both sides.

\displaystyle 9-2x = \frac{1}{81}

Multiply by 81 on both sides to eliminate the fraction.

\displaystyle 81(9-2x )= \frac{1}{81} \cdot 81

\displaystyle 729-162x=1

Subtract 729 from both sides.

\displaystyle 729-162x-729=1-729

\displaystyle -162x = -728

Divide by negative 162 on both sides.

\displaystyle \frac{-162x}{-162} =\frac{ -728}{-162}

Reduce the fractions.  Double negatives will negate, turning the answer positive.

\displaystyle \frac{ -728}{-162} =\frac{364\times 2}{81\times 2}

The answer is:  \displaystyle \frac{364}{81}

Example Question #68 : Solving Radical Equations

Evaluate:  \displaystyle 3\sqrt[4]{4-2x}-4=2

Possible Answers:

\displaystyle -8

\displaystyle -\frac{1}2

\displaystyle -6

\displaystyle -2

\displaystyle -10

Correct answer:

\displaystyle -6

Explanation:

Isolate the radical.  Add four on both sides.

\displaystyle 3\sqrt[4]{4-2x}-4+4=2+4

\displaystyle 3\sqrt[4]{4-2x}=6

Divide by three on both sides.  The equation becomes:

\displaystyle \sqrt[4]{4-2x}= 2

Raise both sides by four.

\displaystyle (\sqrt[4]{4-2x}) ^4= 2^4

\displaystyle 4-2x = 16

Subtract four on both sides.

\displaystyle 4-2x -4= 16-4

\displaystyle -2x=12

Divide by negative two on both sides.

\displaystyle \frac{-2x}{-2}=\frac{12}{-2}

The answer is:  \displaystyle -6

Example Question #69 : Solving Radical Equations

Solve the equation:  \displaystyle \frac{\sqrt[3]{5x-2}}{6} = \frac{1}{2}

Possible Answers:

\displaystyle \frac{29}{5}

\displaystyle 346

\displaystyle -\frac{11}{27}

\displaystyle \frac{11}{27}

\displaystyle \frac{514}{5}

Correct answer:

\displaystyle \frac{29}{5}

Explanation:

Multiply by six on both sides of the equation.

\displaystyle \frac{\sqrt[3]{5x-2}}{6} \cdot 6= \frac{1}{2} \cdot 6

The equation becomes:

\displaystyle \sqrt[3]{5x-2} =3

Cube both sides to eliminate the radical.

\displaystyle (\sqrt[3]{5x-2}) ^3=3^3

\displaystyle 5x-2 = 27

Add two on both sides.

\displaystyle 5x-2 +2= 27+2

\displaystyle 5x=29

Divide by five on both sides.

\displaystyle \frac{5x}{5}=\frac{29}{5}

The answer is:  \displaystyle \frac{29}{5}

Example Question #70 : Solving Radical Equations

Solve the radical equation:  \displaystyle \sqrt{-6x-5}-7 = 10

Possible Answers:

\displaystyle -\frac{49}{11}

\displaystyle -49

\displaystyle -\frac{7}{3}

\displaystyle \textup{No solution.}

\displaystyle -\frac{1}{7}

Correct answer:

\displaystyle -49

Explanation:

Add seven on both sides.

\displaystyle \sqrt{-6x-5}-7 +7= 10+7

\displaystyle \sqrt{-6x-5} = 17

Square both sides.  This will eliminate the radical.

\displaystyle (\sqrt{-6x-5})^2= 17^2

\displaystyle -6x-5 = 289

Add five on both sides.

\displaystyle -6x-5 +5= 289+5

\displaystyle -6x=294

Divide both sides by negative 6 and reduce the fraction.

\displaystyle \frac{-6x}{-6}=\frac{294}{-6}

The answer is:  \displaystyle -49

Example Question #387 : Radicals

Solve the equation:  \displaystyle \sqrt[3]{3x} = \frac{2}{3}

Possible Answers:

\displaystyle \frac{8}{9}

\displaystyle \frac{16}{81}

\displaystyle \frac{1}{3}

\displaystyle \frac{8}{81}

\displaystyle \frac{2}{27}

Correct answer:

\displaystyle \frac{8}{81}

Explanation:

Cube both sides of the equation.

\displaystyle (\sqrt[3]{3x}) ^3= (\frac{2}{3})^3

This will eliminate the radical on the left side.


\displaystyle 3x= (\frac{2}{3})(\frac{2}{3})(\frac{2}{3})

\displaystyle 3x= \frac{8}{27}

Divide by three on both sides.  This is similar to multiplying one-third on both sides.

\displaystyle 3x \times \frac{1}{3}= \frac{8}{27} \times \frac{1}{3}=\frac{8}{81}

The answer is:  \displaystyle \frac{8}{81}

Example Question #381 : Radicals

Solve the radical equation:  \displaystyle 3-\sqrt[3]{2-x} = -1

Possible Answers:

\displaystyle \textup{No solution.}

\displaystyle 62

\displaystyle -6

\displaystyle -62

\displaystyle 6

Correct answer:

\displaystyle -62

Explanation:

Subtract both sides by three.

\displaystyle 3-\sqrt[3]{2-x} -3= -1-3

The equation becomes: 

\displaystyle -\sqrt[3]{2-x} =-4

Divide both sides by negative one.

\displaystyle \frac{-\sqrt[3]{2-x} }{-1}=\frac{-4}{-1}

\displaystyle \sqrt[3]{2-x} =4

Cube both sides to eliminate the radical.

\displaystyle (\sqrt[3]{2-x}) ^3=4^3

\displaystyle 2-x = 64

Add \displaystyle x on both sides.

\displaystyle 2-x +x= 64+x

\displaystyle 2= 64+x

Subtract 64 on both sides.

\displaystyle 2-64= 64+x-64

The answer is:  \displaystyle -62

Example Question #389 : Radicals

Solve the radical equation:  \displaystyle \sqrt[8]{2x-1} =2

Possible Answers:

\displaystyle \frac{255}{2}

\displaystyle \frac{63}{2}

\displaystyle \frac{257}{2}

\displaystyle \frac{17}{2}

\displaystyle \frac{65}{2}

Correct answer:

\displaystyle \frac{257}{2}

Explanation:

Raise both sides by the power of eight to eliminate the radical.

\displaystyle (\sqrt[8]{2x-1} )^8=2^8

Simplify both sides.

\displaystyle 2x-1=256

Add one on both sides.

\displaystyle 2x-1+1=256+1

\displaystyle 2x=257

Divide by two on both sides.

\displaystyle \frac{2x}{2}=\frac{257}{2}

The answer is:  \displaystyle \frac{257}{2}

Example Question #390 : Radicals

Solve:  \displaystyle \frac{1}{\sqrt{3x}} = 4

Possible Answers:

\displaystyle \frac{1}{48}

\displaystyle \frac{16}{3}

\displaystyle 8

\displaystyle \frac{1}{24}

\displaystyle \frac{1}{72}

Correct answer:

\displaystyle \frac{1}{48}

Explanation:

Multiply by \displaystyle \sqrt{3x} on both sides.

\displaystyle \frac{1}{\sqrt{3x}} \cdot \sqrt{3x}= 4 \cdot \sqrt{3x}

\displaystyle 1=4\sqrt{3x}

Divide by 4 on both sides.

\displaystyle \frac{1}{4}=\frac{4\sqrt{3x}}{4}

\displaystyle \frac{1}{4} =\sqrt{3x}

Square both sides to eliminate the radical.

\displaystyle (\frac{1}{4}) ^2=(\sqrt{3x})^2

\displaystyle \frac{1}{16} = 3x

Divide by three on both sides.  This is similar to multiplying both sides by one third.

\displaystyle \frac{1}{16} \cdot \frac{1}{3}= 3x\cdot \frac{1}{3}

The answer is:  \displaystyle \frac{1}{48}

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