To determine why the equation \(-5 = \frac{4 - 3x}{4 - 3x}\) might be undefined, we need to examine the fraction on the right side, \(\frac{4 - 3x}{4 - 3x}\).
This expression is undefined when the denominator is equal to zero. Therefore, we need to find the value of \(x\) that makes the denominator \(4 - 3x\) equal to zero:
\[ 4 - 3x = 0 \]
Solving for \(x\):
\[ 3x = 4 \ x = \frac{4}{3} \]
Thus, the equation \(-5 = \frac{4 - 3x}{4 - 3x}\) is undefined specifically when \(x = \frac{4}{3}\). At this value, both the numerator and the denominator become zero, leading to an indeterminate form \( \frac{0}{0} \). Therefore, the original equation is undefined for \(x = \frac{4}{3}\).