Algebra II : Mathematical Relationships and Basic Graphs

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #51 : Negative Exponents

Evaluate \(\displaystyle (-5)^{-4}\)

Possible Answers:

\(\displaystyle -\frac{1}{625}\)

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

\(\displaystyle -20\)

\(\displaystyle 20\)

\(\displaystyle \frac{1}{625}\)

Correct answer:

\(\displaystyle \frac{1}{625}\)

Explanation:

When expressing negative exponents, we rewrite as such: 

\(\displaystyle x^{-a}=\frac{1}{x^a}\) 

in which \(\displaystyle a\) is the positive exponent raising base \(\displaystyle x\).

\(\displaystyle (-5)^{-4}=\frac{1}{(-5)^4}=\frac{1}{625}\)

Example Question #51 : Negative Exponents

Evaluate \(\displaystyle \frac{1}{2}^{-3}\)

Possible Answers:

\(\displaystyle \frac{1}{8}\)

\(\displaystyle -\frac{1}{6}\)

\(\displaystyle -8\)

\(\displaystyle -\frac{1}{8}\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 8\)

Explanation:

When expressing negative exponents, we rewrite as such: 

\(\displaystyle x^{-a}=\frac{1}{x^a}\) 

in which \(\displaystyle a\) is the positive exponent raising base \(\displaystyle x\).

\(\displaystyle \frac{1}{2}^{-3}=\frac{1}{(\frac{1}{2})^3}=\frac{1}{\frac{1}{8}}=8\)

Example Question #53 : Understanding Exponents

Evaluate \(\displaystyle \frac{1}{6}^{-\frac{1}{2}}\)

Possible Answers:

\(\displaystyle \frac{\sqrt{6}}{6}\)

\(\displaystyle \sqrt{6}\)

\(\displaystyle 6\)

\(\displaystyle -\sqrt{6}\)

\(\displaystyle \frac{1}{36}\)

Correct answer:

\(\displaystyle \sqrt{6}\)

Explanation:

When dealing with fractional exponents, we rewrite as such: 

\(\displaystyle x^\frac{a}{b}=\sqrt[b]{x^a}\) 

in which \(\displaystyle b\) is the index of the radical and \(\displaystyle a\) is the exponent raising base \(\displaystyle a\)

When expressing negative exponents, we rewrite as such: 

\(\displaystyle x^{-a}=\frac{1}{x^a}\) 

in which \(\displaystyle a\) is the positive exponent raising base \(\displaystyle x\).

\(\displaystyle \frac{1}{6}^{-\frac{1}{2}}=\frac{1}{(\sqrt\frac{1}{6})}=\frac{1}{\frac{1}{\sqrt{6}}}=\sqrt{6}\)

Example Question #51 : Exponents

Evaluate \(\displaystyle 12^{-\frac{1}{2}}\)

Possible Answers:

\(\displaystyle \frac{\sqrt{3}}{6}\)

\(\displaystyle \frac{1}{12}\)

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

\(\displaystyle 6\sqrt{3}\)

\(\displaystyle \frac{\sqrt{3}}{2}\)

Correct answer:

\(\displaystyle \frac{\sqrt{3}}{6}\)

Explanation:

When dealing with fractional exponents, we rewrite as such: 

\(\displaystyle x^\frac{a}{b}=\sqrt[b]{x^a}\) 

in which \(\displaystyle b\) is the index of the radical and \(\displaystyle a\) is the exponent raising base \(\displaystyle a\)

When expressing negative exponents, we rewrite as such: 

\(\displaystyle x^{-a}=\frac{1}{x^a}\) 

in which \(\displaystyle a\) is the positive exponent raising base \(\displaystyle x\).

\(\displaystyle 12^{-\frac{1}{2}}=\frac{1}{(\sqrt{12})}=\frac{1}{2{\sqrt{3}}}=\frac{\sqrt{3}}{6}\) 

Remember when getting rid of radicals, just multiply top and bottom by that radical.

Example Question #55 : Understanding Exponents

Evaluate \(\displaystyle 48^{-\frac{2}{3}}\)

Possible Answers:

\(\displaystyle \frac{\sqrt[3]{6}}{24}\)

\(\displaystyle \frac{\sqrt{3}}{24}\)

\(\displaystyle \frac{\sqrt{3}}{6}\)

\(\displaystyle \frac{\sqrt[3]{36}}{16}\)

\(\displaystyle \frac{\sqrt{6}}{16}\)

Correct answer:

\(\displaystyle \frac{\sqrt[3]{6}}{24}\)

Explanation:

When dealing with fractional exponents, we rewrite as such: 

\(\displaystyle x^\frac{a}{b}=\sqrt[b]{x^a}\) 

in which \(\displaystyle b\) is the index of the radical and \(\displaystyle a\) is the exponent raising base \(\displaystyle a\)

When expressing negative exponents, we rewrite as such: 

\(\displaystyle x^{-a}=\frac{1}{x^a}\) 

in which \(\displaystyle a\) is the positive exponent raising base \(\displaystyle x\).

\(\displaystyle 48^{-\frac{2}{3}}=\frac{1}{\sqrt[3]{48^2}}=\frac{1}{\sqrt[3]{2304}}\) 

Let's find a perfect cube which is 

\(\displaystyle 64 =(4^3)\).

\(\displaystyle \frac{1}{\sqrt[3]{2304}}=\frac{1}{\sqrt[3]{64}*\sqrt[3]{36}}=\frac{1}{4\sqrt[3]{36}}\) 

To simplify, we need to multiply top and bottom by an appropriate cubic root. We know \(\displaystyle 36=6^2\) so if we multiply top and bottom by \(\displaystyle \sqrt[3]{6}\) we will get an integer in the denominator.

\(\displaystyle \frac{1}{4\sqrt[3]{36}}*\frac{\sqrt[3]{6}}{\sqrt[3]{6}}=\frac{\sqrt[3]{6}}{4*6}=\frac{\sqrt[3]{6}}{24}\)

Example Question #56 : Understanding Exponents

Evaluate \(\displaystyle 12^{-\frac{3}{4}}\)

Possible Answers:

\(\displaystyle \frac{\sqrt[4]{12}}{8}\)

\(\displaystyle \frac{\sqrt[4]{12}}{12}\)

\(\displaystyle \frac{\sqrt[3]{36}}{16}\)

\(\displaystyle \frac{\sqrt{6}}{12}\)

\(\displaystyle \frac{\sqrt[3]{12}}{12}\)

Correct answer:

\(\displaystyle \frac{\sqrt[4]{12}}{12}\)

Explanation:

When dealing with fractional exponents, we rewrite as such: 

\(\displaystyle x^\frac{a}{b}=\sqrt[b]{x^a}\) 

in which \(\displaystyle b\) is the index of the radical and \(\displaystyle a\) is the exponent raising base \(\displaystyle a\)

When expressing negative exponents, we rewrite as such: 

\(\displaystyle x^{-a}=\frac{1}{x^a}\) 

in which \(\displaystyle a\) is the positive exponent raising base \(\displaystyle x\).

\(\displaystyle 12^{-\frac{3}{4}}=\frac{1}{\sqrt[4]{12^3}}=\frac{1}{\sqrt[4]{1728}}\) 

Let's find a perfect fourth power which is 

\(\displaystyle 16 = (2^4)\).

\(\displaystyle \frac{1}{\sqrt[4]{1728}}=\frac{1}{\sqrt[4]{16}*\sqrt[4]{108}}=\frac{1}{2\sqrt[4]{108}}\) 

To simplify, we need to multiply top and bottom by an appropriate fourth root. We know \(\displaystyle 108=3^3*2^2\).

We need to complete the numbers to the fourth power. It we multiply top and bottom by \(\displaystyle \sqrt[4]{3*2^2}=\sqrt[4]{12}\) we will get an integer in the denominator.

\(\displaystyle \frac{1}{2\sqrt[4]{108}}*\frac{\sqrt[4]{12}}{\sqrt[4]{12}}=\frac{\sqrt[4]{12}}{2*6}=\frac{\sqrt[4]{12}}{12}\)

Example Question #51 : Exponents

Simplify \(\displaystyle (4x^{2}y^{-6})(2x^{-7}y^{^3})\).

Possible Answers:

\(\displaystyle 8x^{5}y^{3}\)

\(\displaystyle \frac{1}{8x^{14}y^{18}}\)

\(\displaystyle \frac{8}{x^{5}y^{3}}\)

\(\displaystyle \frac{1}{8x^{5}y^{3}}\)

\(\displaystyle \frac{8}{x^{14}y^{18}}\)

Correct answer:

\(\displaystyle \frac{8}{x^{5}y^{3}}\)

Explanation:

First multiply the like terms, remembering that when multiplying terms that have exponents, you add the exponents.

\(\displaystyle (4x^{2}y^{-6})(2x^{-7}y^{3})=(4\cdot 2)(x^{2}\cdot x^{-7})(y^{-6}\cdot y^{3})\)

\(\displaystyle =8x^{2-7}y^{-6+3}\)

\(\displaystyle =8x^{-5}y^{-3}\)

Negative exponents indicate that the term should be in the denominator, so the final answer is:

\(\displaystyle \frac{8}{x^{5}y^{3}}\)

Example Question #51 : Understanding Exponents

Simplify:  \(\displaystyle 6^{-2}+3^{-2}\)

Possible Answers:

\(\displaystyle \frac{1}{81}\)

\(\displaystyle \frac{5}{36}\)

\(\displaystyle \sqrt{6}+\sqrt{3}\)

\(\displaystyle \frac{5}{18}\)

\(\displaystyle -3\)

Correct answer:

\(\displaystyle \frac{5}{36}\)

Explanation:

Convert each negative exponent into fractional form.

\(\displaystyle a^{-n} = \frac{1}{a^n}\)

\(\displaystyle 6^{-2}+3^{-2}=\frac{1}{6^2}+\frac{1}{3^2}\)

Simplify the denominators.

\(\displaystyle \frac{1}{36}+\frac{1}{9}\)

Convert the second fraction with a common denominator of 36.

\(\displaystyle \frac{1}{36}+\frac{4}{36}= \frac{5}{36}\)

The answer is:  \(\displaystyle \frac{5}{36}\)

Example Question #51 : Exponents

Evaluate:  \(\displaystyle 2^{-3x}=8\)

Possible Answers:

\(\displaystyle -\frac{2}{3}\)

\(\displaystyle -1\)

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

\(\displaystyle -\frac{8}{3}\)

\(\displaystyle -\frac{1}{4}\)

Correct answer:

\(\displaystyle -1\)

Explanation:

In order to determine the value of x, we will need to convert the base of the right side similar to the left.

Eight is similar to two cubed.  Rewrite the equation.

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

Now that our bases are the same, we can set the exponents equal to each other.

\(\displaystyle -3x=3\)

Divide by negative three on both sides.

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

The answer is:  \(\displaystyle x=-1\)

Example Question #60 : Understanding Exponents

Evaluate:  \(\displaystyle \frac{3x}{3^{-2}}\)

Possible Answers:

\(\displaystyle 9x\)

\(\displaystyle \frac{1}{27x}\)

\(\displaystyle 27x\)

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

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

Correct answer:

\(\displaystyle 27x\)

Explanation:

The negative exponent can be converted into a fraction.

\(\displaystyle a^{-n} = \frac{1}{a^n}\)

Rewrite the fraction.

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

Rewrite the complex fraction using a division sign.

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

Turn the division sign to a multiplication sign and take the reciprocal of the second term.

\(\displaystyle 3x\times \frac{3^2}{1}=3x(9) = 27x\)

The answer is:  \(\displaystyle 27x\)

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