Final answer:
Without a third equation relating x, y, and z, the value of z cannot be determined from the information provided.
Step-by-step explanation:
To find the value of z when x equals t² + 1 and y equals t² - 1, we would need additional information or a relationship between x, y, and z. Since this critical piece of information is not provided in the student's question, we are unable to calculate the value of z solely based on the equations given for x and y. To determine z, a third equation that relates x, y, and z is required.