Thoughtfully split the expression at hand into groups, each group having two terms :
Group 1: 15m - 40 Group 2: <span> -16m2 + 6m3</span>
Pull out from each group separately :
Group 1: (3m - 8) • (5) Group 2: <span> (3m - 8) • (2m2)</span> ------------------- Add up the two groups : <span> (3m - 8) • </span><span> (2m2 + 5)</span> <span>Which is the desired factorization</span>