Question

Factorise:
$m^4-256$

Answer 1

$m^4-256$

$={\left(m^2\right)}^2-{\left(16\right)}^2$

$=(m^2-16)(m^2+16)$

$=(m^2-4^2)(m^2+16)$

$=(m-4)(m+4)(m^2+16)$