Question

(5+y)(5+3y)–(2+3y)(2+5y)+12(y+1)(y–1)–9

Answer 1

(25+15y+5y+3y^2)-(4+10y+6y+15y^2)+(12y^2-12y+12y-12)-9=
(25+20y+3y^2)-(4+16y+15y^2)+(12y^2-0-12)-9=
25+20y+3y^2-4-16y-15y^2+12y^2-12-9=
(25-4-12-9)+(20y-16y)+(3y^2-15y^2+12y^2)=
0+4y+0=
4y