Chapter 1: Problem 24
Evaluate each expression without using a calculator. $$ (-27)^{2 / 3} $$
Short Answer
Expert verified
The expression \((-27)^{2/3}\) evaluates to 9.
Step by step solution
01
Understand the Expression
The expression \((-27)^{2/3}\) involves taking the cube root of -27 and then squaring the result. This is because the exponent \(2/3\) can be interpreted as the cube root (denominator) of (-27), which is then raised to the power of 2 (numerator).
02
Evaluate the Cube Root
Find \((-27)^{1/3}\), which is the cube root of -27. Since \((-3)^3 = -27\), the cube root of -27 is -3.
03
Square the Result
Take the result from Step 2, which is -3, and square it to find \((-3)^2\). Squaring -3 gives 9 since \((-3) imes (-3) = 9\).
04
Combine the Results
Therefore, \((-27)^{2/3}\) simplifies to 9.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cube Roots
A cube root is when you find a number that multiplies by itself three times to equal a given number. When it comes to negative numbers, you can take the cube root without an issue, unlike even roots. This is because the product of a negative times a negative is a positive, and that positive times another negative yields a negative.
For example:
For example:
- The cube root of \(-27\) is \(-3\), since \((-3) \times (-3) \times (-3) = -27\).
- This means that the cube root of a negative number will always be negative.
Fractional Exponents
Fractional exponents offer a concise way to denote roots and powers simultaneously. In the expression \((-27)^{2/3}\), the exponent \(2/3\) indicates both cube root and squaring. The denominator \(3\) tells us to take the cube root, while the numerator \(2\) indicates to square the result.
This is interpreted as:
This is interpreted as:
- First, take the cube root of \(-27\) to get \(-3\).
- Then, take this result and square it to yield \((-3)^2 = 9\).
Negative Numbers
Dealing with negative numbers can seem tricky, especially in the context of exponents and roots. It's essential to remember that multiplying two negative numbers results in a positive number, but multiplying a positive by a negative stays negative.
For instance:
For instance:
- a negative number squared, like \((-3)^2\) results in \(9\).
- However, when you have a cube root of a negative, such as \((-27)^{1/3}\), the result is negative, delivering \(-3\).
Exponentiation Steps
Exponentiation involves raising numbers to powers, which can be simplified using step-by-step techniques for better comprehension. This systematic approach is beneficial for complex numbers or those involving roots or fractional powers.
In the expression \((-27)^{2/3}\), the steps are straightforward:
In the expression \((-27)^{2/3}\), the steps are straightforward:
- Begin by finding the cube root of \(-27\), resulting in \(-3\).
- Then, take this result and square it, which gives \(9\).
- Finally, integrate these operations: cube rooting, followed by squaring. Always tackle the root first, as determined by the denominator of the fractional exponent.