(4m+5n)2+(5m+4n)2
=(4m)2+(5n)2+2×4m×5n+(5m)2+(4n)2+2×5m×4n
=16m2+25n2+40mn+25m2+16n2+40mn
=41m2+41n2+80mn
Hence , this is the answer.
Simplify: (4m+5n)2+(5m+4n)2