Rational exponents evaluate each expression. (a) 27^(1/3) (b) (-8)^(1/3) (c) -(1/8)^(1/3)

Khaleesi Herbert 2020-10-27 Answered

Rational exponents evaluate each expression.
(a) \(\displaystyle{27}^{{{1}\text{/}{3}}}\)
(b) \(\displaystyle{\left(-{8}\right)}^{{{1}\text{/}{3}}}\)
(c) \(\displaystyle-{\left(\frac{1}{{8}}\right)}^{{{1}\text{/}{3}}}\)

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Expert Answer

d2saint0
Answered 2020-10-28 Author has 18870 answers
(a) Definition used:
Definition of rational exponents:
"For any rational exponent m/n in its lowest terms, where m and n are integers and \(\displaystyle{n}>{0}\ \text{we define,}\ \displaystyle{\left({a}\right)}^{{\frac{m}{{n}}}}={\sqrt[{{n}}]{{{\left({a}\right)}^{m}}}}={\left({\sqrt[{{n}}]{{{a}}}}\right)}^{m}.\)
Formula used:
Laws of exponents:
"To raise a power to a new power, multiply the exponents".
\(\displaystyle{\left({a}^{m}\right)}^{n}={a}^{{{m}{n}}}\)
Calculation:
The given expression is \(\displaystyle{27}^{{\frac{1}{{3}}}}.\)
Use the above mentioned definition and simplify the expression as shown below.
\(\displaystyle{27}^{{\frac{1}{{3}}}}={\left({3}\times{3}\times{3}\right)}^{{\frac{1}{{3}}}}\)
\(\displaystyle={\left({3}^{3}\right)}^{{\frac{1}{{3}}}}\)
\(\displaystyle={3}^{{{3}\times\frac{1}{{3}}}}\)
\(= 3\)
Thus, the value of the expression \(\displaystyle{27}^{{\frac{1}{{3}}}}\) is 3.
(b) Use the above definition and formula mentioned in sub part (a) and simplify the expression as shown below.
\(\displaystyle{\left(-{8}\right)}^{{\frac{1}{{3}}}}={\left({\left(-{2}\right)}\times{\left(-{2}\right)}\times{\left(-{2}\right)}\right)}^{{\frac{1}{{3}}}}\)
\(\displaystyle={\left(-{2}\right)}^{{{3}\times\frac{1}{{3}}}}\)
\(\displaystyle={\left(-{2}\right)}^{{{3}\times\frac{1}{{3}}}}\)
\(=\ - 2\)
Thus, the value of the expression \(\displaystyle{\left(-{8}\right)}^{{\frac{1}{{3}}}}\) is (-2).
(c) Use the above definition and formula mentioned in sub part (a) and simplify the expression as shown below.
\(\displaystyle-{\left(\frac{1}{{8}}\right)}^{{\frac{1}{{3}}}}=-{\left(\frac{1}{{2}^{3}}\right)}^{{\frac{1}{{3}}}}\)
\(\displaystyle=-{\left({2}^{ -{{3}}}\right)}^{{\frac{1}{{3}}}}\)
\(\displaystyle=-{\left({2}^{{-{3}\times\frac{1}{{3}}}}\right)}\)
On further simplifications, the following is obtained.
\(\displaystyle-{\left(\frac{1}{{8}}\right)}^{{\frac{1}{{3}}}}=-{\left({2}^{ -{{1}}}\right)}\)
\(\displaystyle={\left(-\frac{1}{{2}}\right)}\)
Thus, the value of the expression \(\displaystyle-{\left(\frac{1}{{8}}\right)}^{{\frac{1}{{3}}}}\ \text{is}\ \displaystyle={\left(-\frac{1}{{2}}\right)}.\)
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