For the first table you need to plug the number given to you for x to the equation 4^-x. For example, a would be 1 because any number to the zeroth power is 1. Remember that a negative exponent will move the numerator to the denominator. For the second table you have to plug the numbers given to you for x into the equation (2/3)^x. For example, you would get 1 for d because any number to the zeroth power is 1.
