$N(x) -M(x)=-5x^{4}-4x^{3}+2x^{2}+8x$
$N(x)=-5x^{4}-4x^{3}+2x^{2}+8x+M(x)=-5x^{4}-4x^{3}+2x^{2}+8x+(3x^{5}-4x^{3}+9x+2)$
$N(x)= 3x^{5}-5x^{4}-8x^{3}+2x^{2}+17x+2$
$Q(x)+M(x)=3x^{4}-2x^{3}+9x^{2}-7$
$Q(x)=3x^{4}-2x^{3}+9x^{2}-7-M(x)=3x^{4}-2x^{3}+9x^{2}-7-(3x^{5}-4x^{3}+9x+2)$
$Q(x)=-3x^{5}+3x^{4}+2x^{3}+9x^{2}-9x-9$