Problem 80 - Precalculus

Question

Find the modulus of \(z=a,\) where \(a\) is a negative real number.

Step-by-Step Solution

Answer

The modulus of \( z = a \), where \( a \) is negative, is \( -a \).

Step 1: Understanding Modulus of a Real Number

The modulus of a real number refers to its absolute value, regardless of its sign. For any real number, positive or negative, the modulus is the number without its sign.

Step 2: Apply the Definition of Modulus

For a given negative real number, such as our variable \(a\), the modulus is determined by removing the negative sign. This can be represented as \(|a| = -a\) when \(a < 0\).

Step 3: Conclude with Specific Example

If \(a\) is a specific negative value, say \(-5\), the modulus \(|a|\) would be \(5\). This shows that regardless of \(a\)'s value being negative, the modulus is the same as the positive counterpart.

Key Concepts

absolute value

The absolute value of a number is essentially its distance from zero on the number line, without considering its direction. This means that both positive and negative numbers have the same absolute value if they are the same distance from zero. For instance, both 3 and -3 have an absolute value of 3 because they are both three units away from zero on the number line.

Mathematically, the absolute value of a number \( x \) is represented as \( |x| \). The formula is straightforward:

• If \( x \) is positive or zero, \( |x| = x \).
• If \( x \) is negative, \( |x| = -x \).

This ensures that the result is always non-negative, capturing the essence of the number's magnitude.

negative real number

Negative real numbers are those numbers less than zero and are located to the left side of zero on the number line. Typically represented with a minus (-) sign, these numbers can include integers, decimals, and fractions.

Understanding how negative real numbers work is crucial for grasping the concept of absolute value. For instance, when working with negative real numbers, such as \(-7.5\), the modulus or absolute value can be simply found by removing the negative sign, resulting in 7.5. This operation effectively only considers how far the number is from zero, not the direction.

The clarity in dealing with negative numbers helps in various mathematical operations and problem-solving where understanding the magnitude without the sign is beneficial.

properties of modulus

The modulus, or absolute value, has several fundamental properties that make it useful in mathematics. These properties help in solving equations and understanding mathematical functions. Let's outline some key properties:

• Non-negativity: The modulus \(|x|\) is always non-negative. This means for any real number \(x\), \(|x| \geq 0\).
• Identity: The modulus of zero is zero. That is, \(|0| = 0\).
• Symmetry: The modulus of a number is equal to its opposite. Meaning \(|x| = |-x|\). For example, \(|5| = 5\) and \(|-5| = 5\).
• Triangle Inequality: For any two real numbers \(a\) and \(b\), \(|a + b| \leq |a| + |b|\). This property is particularly useful in real analysis and vector spaces.

These properties are fundamental in ensuring that calculations involving modulus are consistent and adhere to mathematical principles.