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

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Answer 1 · 2018-05-17T22:02:01

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

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

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