Answer :

[tex](-7x^2-7x-7)-[(7x^3-9x^2-20)+(4x-11)]]=\\=-7x^2-7x-7-(7x^3-9x^2-20+4x-11)=\\=-7x^2-7x-7-7x^3+9x^2+20-4x+11=-7x^3+2x^2-11x+24\\\\ (5x^4+8x^2+2)+7(5x^4-3x^2)=5x^4+8x^2+2+35x^4-21x^2=\\=39x^4-13x^2+2[/tex]