Learn about letters or numbers to the power of zero, negative indices. ... In this example the number 4 is called the index (plural indices) and the number represented by 𝑛 is the base.

Any number or variable with a negative index, can be written as 1 over that number or variable, to the equivalent positive index. So, for example, x to the negative 4 equals 1 over x to the 4, 2x ...