Question

What is the rule for subtraction with exponents: ie r^5 - r^4?

Answer 1

There is no rule to write it as one term. See explanation.

Explanation:

If you want to write this expression as a single power `r^a` then there is no such rule for subtraction. Only power, multiplication or division can be written in such way.

Only thing you can do is to factorize the expression.

`r^5-r^4=r^4*(r-1)`