6m3 - 16m2 + 15m - 40 Simplify ————————————————————— 2m2 + 5 Checking for a perfect cube : 4.1   6m3 - 16m2 + 15m - 40 is not a perfect cube 
Trying to factor by pulling out : 4.2  Factoring:  6m3 - 16m2 + 15m - 40 
Thoughtfully split the expression at hand into groups, each group having two terms :
Group 1: 15m - 40 
Group 2:  -16m2 + 6m3 
Pull out from each group separately :
Group 1: (3m - 8) • (5)
Group 2:  (3m - 8) • (2m2)
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Add up the two groups :
  (3m - 8) •  (2m2 + 5) 
Which is the desired factorization3m-8 is the answer