= (10-m)^2 x (10-m)^2
= (10-m)(10-m)(10-m)(10-m)
= (100 - 20m + m^2)(100 - 20m + m^2)
= 10000 - 2000m + 100m^2 - 2000m + 400m^2 - 20m^3 + 100m^2 - 20m^3 + m^4
= 10000 - 4000m + 600m^2 - 40m^3 + m^4