4) 3p(p-4)-(p-2)(p+2)= 3p₂-12p-p₂+4=2p₂-12p+4
5) (c-3)₂-2c(c-2)=c₂-6c+9-2c₂+4= -c₂-6c+13
6) 10py+5(p-y)₂=10py+5p₂-10py+5y₂=5p₂+5y₂
7)a₂-25= (a-5)(a+5)
8)49y₂-4a₂=(7y-4a)(7y+4a)
9)x₂-4ax+4a₂=(x-2a)₂
10)36c₃-c=c(36c₂-1)=c(6c-1)(6c+1)
-7z₂+(3z-4)₂-2(4+z)(z-4)= -7z₂+9z₂-24z+16-2z₂+32= -24z+16+32= -24z+48= 48-24z
a₂-14a+49; a=407
(a-7)₂= (407-7)₂=400₂=160000