Algebra II : Algebra II

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #105 : Solving Radical Equations

Solve the equation:  \(\displaystyle \frac{\sqrt{-3-7x} }{-3}= -9\)

Possible Answers:

\(\displaystyle \textup{No solution.}\)

\(\displaystyle -\frac{726}{7}\)

\(\displaystyle -\frac{732}{7}\)

\(\displaystyle \frac{732}{7}\)

\(\displaystyle \frac{12}{7}\)

Correct answer:

\(\displaystyle -\frac{732}{7}\)

Explanation:

Multiply by negative three on both sides.

\(\displaystyle \frac{\sqrt{-3-7x} }{-3} \cdot -3= -9 \cdot -3\)

\(\displaystyle \sqrt{-3-7x} = 27\)

Square both sides.

\(\displaystyle (\sqrt{-3-7x}) ^2= (27)^2\)

\(\displaystyle -3-7x = 729\)

Add three on both sides.

\(\displaystyle -3-7x +3= 729+3\)

\(\displaystyle -7x=732\)

Divide by negative seven on both sides.

\(\displaystyle \frac{-7x}{-7}=\frac{732}{-7}\)

The answer is:  \(\displaystyle -\frac{732}{7}\)

Example Question #106 : Solving Radical Equations

Solve the equation:  \(\displaystyle \frac{5}{\sqrt{5x}} = 10\)

Possible Answers:

\(\displaystyle \frac{1}{200}\)

\(\displaystyle \frac{\sqrt{5}}{10}\)

\(\displaystyle \frac{1}{20}\)

\(\displaystyle \frac{5}{4}\)

\(\displaystyle \frac{1}{10}\)

Correct answer:

\(\displaystyle \frac{1}{20}\)

Explanation:

Multiply the denominator on both sides to eliminate the fraction.

\(\displaystyle \frac{5}{\sqrt{5x}} \cdot \sqrt{5x}= 10 \cdot \sqrt{5x}\)

The equation becomes:

\(\displaystyle 5=10\sqrt{5x}\)

Square both sides.

\(\displaystyle 5^2=(10\sqrt{5x})^2\)

\(\displaystyle 25= 100(5x)\)

\(\displaystyle 25 =500x\)

Divide by 500 on both sides.

\(\displaystyle \frac{25}{500} =\frac{500x}{500}\)

Reduce both fractions.

The answer is:  \(\displaystyle \frac{1}{20}\)

Example Question #101 : Solving Radical Equations

Solve:  \(\displaystyle \sqrt{x}-5 = \frac{1}{5}\)

Possible Answers:

\(\displaystyle \frac{24}{5}\)

\(\displaystyle \frac{2}{25}\)

\(\displaystyle \frac{676}{25}\)

\(\displaystyle \frac{50}{3}\)

\(\displaystyle \frac{1}{25}\)

Correct answer:

\(\displaystyle \frac{676}{25}\)

Explanation:

Add 5 on both sides.  This is the same as adding \(\displaystyle \frac{25}{5}\) on both sides.

\(\displaystyle \sqrt{x}-5 +5= \frac{1}{5}+\frac{25}{5}\)

\(\displaystyle \sqrt{x} = \frac{26}{5}\)

To eliminate the radical, we must square both sides of the equation.

\(\displaystyle (\sqrt{x}) ^2=( \frac{26}{5})^2\)

The answer is:  \(\displaystyle \frac{676}{25}\)

Example Question #421 : Radicals

Solve:  \(\displaystyle \frac{14}{\sqrt[4]{2x}+3} =4\)

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle \frac{1}{16}\)

\(\displaystyle \textup{The answer is not given.}\)

\(\displaystyle \frac{1}{32}\)

\(\displaystyle \frac{7}{8}\)

Correct answer:

\(\displaystyle \frac{1}{32}\)

Explanation:

Multiply the denominator on both sides to eliminate the denominator.

\(\displaystyle \frac{14}{\sqrt[4]{2x}+3} \cdot (\sqrt[4]{2x}+3)=4\cdot (\sqrt[4]{2x}+3)\)

Simplify both sides.

\(\displaystyle 14 = 4\sqrt[4]{2x}+12\)

Subtract 12 from both sides.

\(\displaystyle 14-12 = 4\sqrt[4]{2x}+12-12\)

The equation becomes:

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

Divide by 4 on both sides.

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

\(\displaystyle \frac{1}{2}=\sqrt[4]{2x}\)

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

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

\(\displaystyle \frac{1}{16} = 2x\)

Multiply by one half on both sides to isolate \(\displaystyle x\).

\(\displaystyle \frac{1}{16}\cdot \frac{1}{2} = 2x\cdot \frac{1}{2}\)

The answer is:  \(\displaystyle \frac{1}{32}\)

Example Question #101 : Solving Radical Equations

Solve:  \(\displaystyle 5-3\sqrt{9x} = -2\)

Possible Answers:

\(\displaystyle -\frac{1}{9}\)

\(\displaystyle \frac{7}{9}\)

\(\displaystyle \textup{No solution.}\)

\(\displaystyle \frac{49}{81}\)

\(\displaystyle \frac{49}{3}\)

Correct answer:

\(\displaystyle \frac{49}{81}\)

Explanation:

Subtract five from both sides of the equation.

\(\displaystyle 5-3\sqrt{9x} -5= -2-5\)

\(\displaystyle -3\sqrt{9x} = -7\)

Divide by negative three on both sides.

\(\displaystyle \frac{-3\sqrt{9x} }{-3}=\frac{ -7}{-3}\)

\(\displaystyle \sqrt{9x} = \frac{7}{3}\)

Square both sides.

\(\displaystyle (\sqrt{9x}) ^2=( \frac{7}{3})^2\)

Simplify both sides.

\(\displaystyle 9x =\frac{49}{9}\)

Multiply by one-ninth on both sides.

\(\displaystyle 9x \cdot \frac{1}{9}=\frac{49}{9}\cdot \frac{1}{9}\)

The answer is:  \(\displaystyle \frac{49}{81}\)

Example Question #102 : Solving Radical Equations

Solve the equation:  \(\displaystyle \frac{\sqrt{2x}}{\sqrt5} = \frac{\sqrt6}{\sqrt x}\)

Possible Answers:

\(\displaystyle \frac{\sqrt{22}}{2}\)

\(\displaystyle 15\)

\(\displaystyle \pm 2\sqrt{15}\)

\(\displaystyle \pm 15\)

\(\displaystyle \pm\frac{\sqrt{22}}{2}\)

Correct answer:

\(\displaystyle 15\)

Explanation:

Cross multiply both sides.

\(\displaystyle \sqrt{2x}(\sqrt x) =(\sqrt5)(\sqrt6)\)

\(\displaystyle \sqrt{2x^2} = \sqrt{30}\)

Square both sides in order to cancel the radicals.

\(\displaystyle (\sqrt{2x^2}) ^2= (\sqrt{30})^2\)

\(\displaystyle 2x^2 = 30\)

Divide by 2 on both sides.

\(\displaystyle \frac{2x^2}{2} = \frac{30}{2}\)

\(\displaystyle x^2=15\)

Square root both sides.

\(\displaystyle \sqrt{x^2} = \sqrt{15}\)

\(\displaystyle x=\pm 15\)

Only \(\displaystyle x=15\) will satisfy the original equation.

The answer is:  \(\displaystyle 15\)

Example Question #111 : Solving And Graphing Radicals

If \(\displaystyle \sqrt{2x+3}-5 = -2\), then \(\displaystyle x=\) ?

Possible Answers:

-3

1

-4

4

3

Correct answer:

3

Explanation:

We will begin by adding 5 to both sides of the equation. 

\(\displaystyle \\\sqrt{2x+3}-5+5 = -2+5\)

\(\displaystyle \sqrt{2x+3} = 3\)

Next, let's square both sides to eliminate the radical.

\(\displaystyle (\sqrt{2x+3})^2 = 3^2\)

\(\displaystyle 2x+3 = 9\)

Finally, we can solve this like a simple two-step equation. Subtract 3 from both sides of the equation.

\(\displaystyle 2x+3-3 = 9-3\)

\(\displaystyle 2x=6\)

Now, divide each side by 2. 

\(\displaystyle \frac{2x}{2}=\frac{6}{2}\)

\(\displaystyle x=3\)

Finally, check the solution to make sure that it results in a true statement.

\(\displaystyle \sqrt{2(3)+3}=3\)

\(\displaystyle \sqrt{9}=3\)

\(\displaystyle 3=3\)

Example Question #1666 : Mathematical Relationships And Basic Graphs

Solve for \(\displaystyle x\):

\(\displaystyle x - 2\sqrt{x} = 3\)

Possible Answers:

\(\displaystyle -1\) or \(\displaystyle 3\)

\(\displaystyle 1\) or \(\displaystyle 9\)

\(\displaystyle 3\)

\(\displaystyle 9\)

\(\displaystyle 16, 9\)

Correct answer:

\(\displaystyle 9\)

Explanation:

When working with radicals, a helpful step is to square both sides of an equation so that you can remove the radical sign and deal with a more classic linear or quadratic equation. But of course if you were to simply square both sides first here, you would still end up with radical signs, as were you to FOIL the left side you wouldn't eliminate the radicals.  So a good first step is to add \(\displaystyle 2\sqrt{x}\) and subtract \(\displaystyle 3\) from both sides so that you get:

 

\(\displaystyle x-3=2{\sqrt{x}}\)

 

Now when you square both sides, you'll eliminate the radical on the right-hand side and yield:

 

\(\displaystyle x^2-6x+9=4x\)

Then when you subtract \(\displaystyle 4x\) from both sides to set up a quadratic equalling zero, you have a factorable quadratic:

 

\(\displaystyle x^2-10x+9=0\)

This factors to:

\(\displaystyle (x-9)(x-1)=0\)

Which would seem to yield solutions of \(\displaystyle x=9\) and \(\displaystyle x=1\).  However, when you're solving for quadratics it's always important to plug your solutions back into the original equation to check for extraneous solutions.  Here if you plug in \(\displaystyle x=9\) the math holds: \(\displaystyle 9-2{\sqrt{9}}=3\) because \(\displaystyle 2\sqrt{9}=2(3)=6\), and \(\displaystyle 9-6=3\).

 

But if you plug in \(\displaystyle x=1\), you'll see that the original equation is not satisfied: \(\displaystyle 1-3\neq 2\sqrt{1}\) because \(\displaystyle -2\) does not equal \(\displaystyle 2\).  Therefore the only proper answer is \(\displaystyle x=9\).

 

Example Question #111 : Solving And Graphing Radicals

Solve for \(\displaystyle x\):

\(\displaystyle \sqrt{x-3} = x - 5\)

Possible Answers:

No solution

\(\displaystyle 7\) or \(\displaystyle 4\)

\(\displaystyle 4\) or \(\displaystyle 1\)

\(\displaystyle \frac{-1 \pm \sqrt{89}}{2 }\)

\(\displaystyle 2\) or \(\displaystyle -1\)

Correct answer:

\(\displaystyle 7\) or \(\displaystyle 4\)

Explanation:

To solve, first square both sides:

\(\displaystyle \sqrt{x-3}^2 = (x-5)^2\) squaring the left side just givs x - 3. To square the left side, use the distributite property and multiply \(\displaystyle (x-5)(x-5)\):

\(\displaystyle x - 3 = x^2 - 10x + 25\) This is a quadratic, we just need to combine like terms and get it equal to 0

\(\displaystyle 0 = x^2 -11x + 28\) now we can solve using the quadratic formula:

\(\displaystyle x = \frac{11 \pm \sqrt{11^2 - 4*1*28}}{2 } = \frac{11 \pm \sqrt {121 - 112}}{2 } = \frac{11 \pm \sqrt{9 }}{2} = \frac{11 \pm 3 }{2}\)

This gives us 2 potential answers:

\(\displaystyle x = \frac{11 + 3 }{2 } = \frac{14 }{2} = 7\) and

\(\displaystyle x = \frac{11 - 3 }{ 2 } = \frac{8}{2} = 4\)

Example Question #421 : Radicals

State the domain of the function: 

\(\displaystyle y=\sqrt{4x+3}\)

Possible Answers:

\(\displaystyle x\leq0\)

\(\displaystyle x\geq\frac{3}{4}\) 

 

\(\displaystyle x\geq-\frac{3}{4}\)

 

\(\displaystyle x\geq -\frac{4}{3}\)

\(\displaystyle x\geq0\)

Correct answer:

\(\displaystyle x\geq-\frac{3}{4}\)

 

Explanation:

Since the expression under the radical cannot be negative,

\(\displaystyle 4x+3\geq0\).

Solve for x:

\(\displaystyle x\geq-\frac{3}{4}\)

This is the domain, or possible \(\displaystyle x\) values, for the function.

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