Final answer:
The expression (x^2 - 4) / (9x + 4) is undefined for x = -4/9 because that value would cause a division by zero in the denominator.
Step-by-step explanation:
The student is asking for which values of x is the expression (x^2 - 4) / (9x + 4) undefined. A mathematical expression is undefined when its denominator equals zero because division by zero is not allowed. Therefore, we must find the value of x that makes the denominator 0. In this case, we set the denominator 9x + 4 equal to zero and solve for x.
9x + 4 = 0
9x = -4
x = -4/9
The expression is undefined when x = -4/9 because substituting x with -4/9 leads to a denominator of zero.