1) 25a^2 - (a+3)^2= 25a^2 - (a^2 + 6a + 9)= 25a^2 - a^2 - 6a - 9= 24a^2 - 6a - 9
2) 16^4 - 81= 256^2 - 81= 65536 - 81= 65455
3) 27m^3 + n^= 27m^3 + n
4) 3a^2 - b - a^2 - b= 2a^2 - 2b
1) 25a^2 - (a+3)^2
= 25a^2 - (a^2 + 6a + 9)
= 25a^2 - a^2 - 6a - 9
= 24a^2 - 6a - 9
2) 16^4 - 81
= 256^2 - 81
= 65536 - 81
= 65455
3) 27m^3 + n^
= 27m^3 + n
4) 3a^2 - b - a^2 - b
= 2a^2 - 2b