Question

How do you factor `r^4-5r^2+4`?

Answer 1

`(r^2 - 1)(r^2 -4)`

Explanation:

The first factoring is splitting the expression into squared factors, similar to what we do with a quadratic.
`r^4 - 5r^2 + 4 = (r^2 - 1)(r^2 -4)`