1) 2(m - 3)+ m(m - 3) = (m-3)(2+m)
2) na - 5a+nb - 5b = (na - 5a) + (nb - 5b) = a(n-5) + b(n-5) = (n-5)(a+b)
3) xy^2 - by^2 - ax + ab + y^2 - a = (xy^2 - by^2 + y^2) - (ax - ab + a) = y^2(x-b+1)-a(x-b+1) = (x-b+1)(y^2-a)
1) 2(m - 3)+ m(m - 3) = (m-3)(2+m)
2) na - 5a+nb - 5b = (na - 5a) + (nb - 5b) = a(n-5) + b(n-5) = (n-5)(a+b)
3) xy^2 - by^2 - ax + ab + y^2 - a = (xy^2 - by^2 + y^2) - (ax - ab + a) = y^2(x-b+1)-a(x-b+1) = (x-b+1)(y^2-a)