y''=5((7x-3x^(2))^(4))' *(7-6x)+(7x-3x^(2))^(4)*(7-6x)')=
=5(4(7x-3x^(2))^(3)*(7-6x)+(7x-3x^(2))^(4)*(-6))=
=20(7x-3x^(2))^(3)*(7-6x)-30(7x-3x^(2))^(4)=
=(7x-3x^(2))^(3)*(20(7-6x)-30(7x-3x^(2))=
=(7x-3x^(2))^(3)*(140-120x-210x+90x^(2))=
=(7x-3x^(2))^(3)*(90x^(2)-330x+140)=10(7x-3x^(2))^(3)(9x^(2)-33x+14)