Question

Factorise:$25m^2-70mn+49n^2$

Answer 1

$25m^2-70mn+49n^2$

$={\left(5m\right)}^2-2\times 5m\times 7n+{\left(7n\right)}^2$ is of the form $a^2-2ab+b^2={(a-b)}^2$

$={(5m-7n)}^2$