Sure, let's go through the steps to rewrite the expression 1/a^4 using a negative exponent:
Step 1: Identify the base number that is being divided by 1. Here the base number is 'a'.
Step 2: Identify the exponent applied to the base number. Here, the exponent is 4.
Step 3: Rewrite the expression using a negative exponent. Here, the expression 1/a^4 can be rewritten as a^-4.
Therefore, the expression 1/a^4 rewritten using a negative exponent is a^-4, which denotes the reciprocal of the base `a` raised to the positive exponent 4.