Determine factorization for each term. Use prime factorization for the numbers.
8m⁴n = 2³ × m⁴ × n
16mn² = 2⁴ × m × n²
To find the greatest common factor, pick equal factors
equal factors are 2, m, n
then pick the equal factors which have lowest exponential number
2³, m, n
Greatest common factor
2³ × m × n
= 8mn
The greatest common factor is 8mn