How do I solve a problem like this:

Question

p^3m^2/7 + p^2m^3/21 - p^4m/14
Can you please help?

Answer 1

common factor: p^2 m/7

mp^2/7 ( pm+m^2 /2 + p^2/2)

now, consider the ( ) factor out 1/2

1/2 (p^2+2pm+m^2)=1/2 (P+m)^2

so, anwer:

mp^2/14 (p+m)^2

check all that.