Разложите на множители:
1) b^2-c^2-7b-7c
2) a^2+10a+25-y^2

1) b^2-c^2-7b-7c=(b^2-c^2)-(7b+7c)=(b-c)(b+c)-7(b+c)=(b+c)(b-c-7)
2) a^2+10a+25-y^2=(a^2+10a+25)-y^2=(a^2+2*5*a+5^2)-y^2=(a+5)^2-y^2=
  =(a+5+y)(a+5-y)