Final answer:
The value of x that makes the expression 2x - 1 / (x + 5) undefined is x = -5.
Step-by-step explanation:
The given expression 2x - 1 / (x + 5) will be undefined when the denominator (x + 5) equals zero. In mathematics, division by zero is undefined. To find the x-value that causes the denominator to be zero, we set the denominator equal to zero and solve for x:
x + 5 = 0
x = -5
Therefore, when x = -5, the denominator becomes 0, resulting in division by zero, which is undefined in arithmetic and mathematical operations. This means that the expression 2x - 1 / (x + 5) is undefined when x is equal to -5 since division by zero is not a valid mathematical operation.