(-7a^n*b^n)^2*(-ab)^3-[5a^2n*(-a)^3*b^2n*b^3]=49a^2n*b^2n*(-a^3*b^3)-[-5a^(2n+3)*b^(2n+3)]=-49a^(2n+3)*b^(2n+3)+5a^(2n+3)*b^(2n+3)]=-44a^(2n+3)*b^(2n+3)